Mountain bike advice

in message <[email hidden]>, John Burns

(') said:

Until last year I was always an on-road man, tried to do 100 miles a
week but didn't always manage :-)

Then last Jan I got a cheap "Boss" mountian bike from ebay, unwanted
Christmas present at a bargain price. Just to see if I liked off
roading, I do :-) It's a 15 speed (too slow on road by far), full
suspension, awful saddle, dodgy gear change, but it did the job. I
currently do about 50+ miles a week off road on it and nothing's broken
except the rear brake cable (easy fix).

So I'm thinking it's time for an upgrade ;-)

On the wish list are Shimano or similar quality gears, full suspension,
no need for disc brakes as far as i can see, decent saddle. Budget of
200-250ish. I've seen things like Saracen AWOLs for about that new on
ebay.

No.

Don't spend less than a thousand on full suspension, it isn't worth it.
Good suspension costs money, and poor suspension is worse than none. If
£250 is what you've got, get a hardtail.

Quoted message said:

Something lighter would be nice too, I'm fed up half killing myself
lifting it over fences and padlocked gates!

Absolutely. Weight matters.

Quoted message said:

1) Why do some people prefer hardtails for offroad use? I can see how
pedalling might be a bit more efficient but it must be very
uncomfortable (lot of rough tracks up here).

You don't sit down so much. Although you'd be surprised how much
difference front suspension makes to comfort.

Quoted message said:

2) I'm assuming the only real bonus with disc brakes is wet weather
performance. My current bikes brakes are excellent, better than my 600
quid tourer's in fact!

No. The real bonus with /hydraulic/ brakes is sensitivity. The bonus of
disk brakes is in seriously muddy conditions - the disk is further away
from the mud than the rims. But cable operated disk brakes are really no
advantage over V brakes, except in deep mud.

Quoted message said:

3) Anything else that should be on my wish list? I'm fairly new to the
mountain bike game.

Basically, avoid gimmicks. Cheap rear suspension and cable operated disk
brakes count as gimmicks.

Quoted message said:

4) Any specific recommendations?

At that sort of price point, if you're anywhere near Edinburgh (or
Aberdeen or Newcastle) you should go and look at the Edinburgh Bike
Co-op's Revolution Cuillin. It's a basic but honest job for the money.

The Claud Butler Cape Wrath is a bike which has been consistently well
reviewed and has extremely good kit for its price; there are 2005 models
still available at around £300.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

I'm fed up with Life 1.0. I never liked it much and now it's getting
me down. I think I'll upgrade to MSLife 97 -- you know, the one that
comes in a flash new box and within weeks you're crawling with bugs.

"John Burns" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

1) Why do some people prefer hardtails for offroad use? I can see how
pedalling might be a bit more efficient but it must be very
uncomfortable (lot of rough tracks up here).

Hardtails (and rigids) give more direct feedback therefore feeling livelier
and can also be lighter. Whether you want this extra feedback is a personal
choice, I don't ;-)

For a given price a hardtail will be of better quality than a full sus and
frankly at your chosen price point any full suspension bike is likely to be
Not Very Good and probably no better than the Boss you want to replace.

Quoted message said:

2) I'm assuming the only real bonus with disc brakes is wet weather
performance. My current bikes brakes are excellent, better than my 600
quid tourer's in fact!

Pretty much spot on. But when the going gets wet on a hilly route *good*
discs are in another league to rim brakes and as a bonus your rims don't
wear through on the braking surfaces*.
I've just completed 2 years with Hope hydraulic discs after 14 years of
cantis & linear (vee) pull brakes and consider them one of the best upgrades
I've made. Having brakes that do exactly what you want them to at the
precise moment you want them to enhances the whole riding experienceas as
well as relieving wrist ache on long descents.
*Two years of rim brake use would require new rims in my normal usage, not
so bad if you can do it yourself (I actually enjoy it) but still an expense
to offset against the purchase price of discs.
--
Pete
http:[email hidden]/Stuff

John Burns said:

Until last year I was always an on-road man, tried to do 100 miles a
week but didn't always manage :-)

Then last Jan I got a cheap "Boss" mountian bike from ebay, unwanted
Christmas present at a bargain price. Just to see if I liked off
roading, I do :-) It's a 15 speed (too slow on road by far), full
suspension, awful saddle, dodgy gear change, but it did the job. I
currently do about 50+ miles a week off road on it and nothing's broken
except the rear brake cable (easy fix).

So I'm thinking it's time for an upgrade ;-)

Sounds familiar to me, I bought cheap from Halfords just to see if I
like it, and I do too!

Quoted message said:

On the wish list are Shimano or similar quality gears, full suspension,
no need for disc brakes as far as i can see, decent saddle. Budget of
200-250ish. I've seen things like Saracen AWOLs for about that new on
ebay.

Something lighter would be nice too, I'm fed up half killing myself
lifting it over fences and padlocked gates!

1) Why do some people prefer hardtails for offroad use? I can see how
pedalling might be a bit more efficient but it must be very
uncomfortable (lot of rough tracks up here).

From what I've read (and i'm no expert, I'm sure one will be along to
correct and glaring errors I make) you cannot buy a decent full
suspension for under 600 of her majestys pound notes.

Hardtails are also lighter (generally) as there is no rear suspension
to drag around.

Quoted message said:

2) I'm assuming the only real bonus with disc brakes is wet weather
performance. My current bikes brakes are excellent, better than my 600
quid tourer's in fact!

Hydraulic discs are apparently the dogs bananas but a cable disc will
have not better performance than good v brakes. The benfit is that
they will not clog up with mud and forest tat like v brakes do.

Quoted message said:

3) Anything else that should be on my wish list? I'm fairly new to the
mountain bike game.

Couple of things I've learn from looking over the past couple of
months is that cheap aluminium is as heavy as steel and if you buy
secondhand then check the frame for cracks or repairs first.You need
21 gears minimum, 18 or less and it's an economy bike.

Quoted message said:

4) Any specific recommendations?

I pick up my new GT avanlanche 2.0 (2005 model at knock down price of
£250) next friday.

Have a look at the following makes: GT, specialized, claud butler etc.
on ebay to find something you like the look of in your price range,
find a local shop to look at one up close, pick your frame size, test
ride if possible and then buy on ebay if it's cheaper!

Hope even a little of that helps and I haven't made myself sound too
stupid being new to this myself 🙂

Cheryl

"John Burns" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Until last year I was always an on-road man, tried to do 100 miles a
week but didn't always manage :-)

Then last Jan I got a cheap "Boss" mountian bike from ebay, unwanted
Christmas present at a bargain price. Just to see if I liked off
roading, I do :-) It's a 15 speed (too slow on road by far), full
suspension, awful saddle, dodgy gear change, but it did the job. I
currently do about 50+ miles a week off road on it and nothing's broken
except the rear brake cable (easy fix).

So I'm thinking it's time for an upgrade ;-)

On the wish list are Shimano or similar quality gears, full suspension,
no need for disc brakes as far as i can see, decent saddle. Budget of
200-250ish. I've seen things like Saracen AWOLs for about that new on
ebay.

To be honest, for this price I do not think you will be getting much
quality. Up your budget to about 700 - 900 - or perhaps even a tad higher -
and have a look at the offerings by Marin, Specilaised, Muddy Fox, Scott
etc. Its probably best to avoid complicated linkages and, in my view, find
something with a "proper" downtube such as the Marins have, rather than
something where the seat post fouls the suspension if you drop the seat.

Quoted message said:

Something lighter would be nice too, I'm fed up half killing myself
lifting it over fences and padlocked gates!

See above Hardtails are lighter, you can i think still get something with a
decent Alu frame for 300 - 350?

Quoted message said:

1) Why do some people prefer hardtails for offroad use? I can see how
pedalling might be a bit more efficient but it must be very
uncomfortable (lot of rough tracks up here).

They are simpler, less maintenance, and as you say some people prefer not to
lose pedalling effort through the rear spring. I use a squidgy seatpost on
mine (A Scott Purgatory, few years old suitable for "light trail use",
hardtail and, sorry to say, with a luggage rack - which you can't really use
on a full susser)

Quoted message said:

2) I'm assuming the only real bonus with disc brakes is wet weather
performance. My current bikes brakes are excellent, better than my 600
quid tourer's in fact!

Biggest bonus of disc brakes for my money is - you don't wear out the rims,
which can happen frighteningly quickly off-roading, and if you get a slight
dent in the rim, the brakes aren't affected. And of course less effect on
braking from mud etc. in the wet, as you say.

Quoted message said:

3) Anything else that should be on my wish list? I'm fairly new to the
mountain bike game.

Hard Hat!! - plus water bottle holders and something to stop the mud getting
all over them, and the usual pump etc. And a shcok pump if you have an air
shock on the bike.

Quoted message said:

4) Any specific recommendations?

See above - or go hardtail from the same manufacturers and save a few bob

Quoted message said:

--
Who needs a life when you've got Unix? :-)
Email: [email hidden], John G.Burns B.Eng, Bonny Scotland
Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage!
Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html
www.Strathspey.co.uk - Quality Binoculars at a Sensible price

Cheryl said:

Sounds familiar to me, I bought cheap from Halfords just to see if I
like it, and I do too!

I got a £130 hardtail with front cable disc from Halfords and it was
brilliant for the first few months. 1000 miles later and it's rideable
but not quite as nice. Chain has suddenly started going rusty despite
a regular dose of oil and it's not worth replacing any more bits - may
as well get a new bike!

pete

Simon Brooke said:

Cheap rear suspension and cable operated disk
brakes count as gimmicks.

Most people would disagree with you as far as cable disks are concerned.
A good set of cable disk brakes is as good as a hydraulic set, and a lot
less trouble. They have the same advantages, good performance in water
and mud, excellent stopping power etc., and the added advantage that you
don't have to mess with hydraulic fluid.

I recommend that the OP head over to the forum at
www.singletrackworld.com and ask his quetsion there.

Mr B;

--
Encrypted e-mail address. Click to mail me:
<http://cerbermail.com/?nKYh3qN4YG>

R. Murphy said:

Biggest bonus of disc brakes for my money is - you don't wear out the rims,
which can happen frighteningly quickly off-roading, and if you get a slight
dent in the rim, the brakes aren't affected.

Absolutely - you can ride home on a seriously buckled rim.

Quoted message said:

Quoted message said:

3) Anything else that should be on my wish list? I'm fairly new to the
mountain bike game.

Quoted message said:

Hard Hat!! - plus water bottle holders

I'd suggest a Camelbak, or a cheap knock-off.

Mr B;

--
Encrypted e-mail address. Click to mail me:
<http://cerbermail.com/?nKYh3qN4YG>

You can get some fab deals from buying from advertisements in the Mountain
Bike UK magazimes or equivalent - the only disadvantage is that you can't
try before you buy. If you have an idea of the type and size of the bike,
you can make a real killing with the proces compared to shops.

Hope this helps :-)

"John Burns" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Until last year I was always an on-road man, tried to do 100 miles a
week but didn't always manage :-)

Then last Jan I got a cheap "Boss" mountian bike from ebay, unwanted
Christmas present at a bargain price. Just to see if I liked off
roading, I do :-) It's a 15 speed (too slow on road by far), full
suspension, awful saddle, dodgy gear change, but it did the job. I
currently do about 50+ miles a week off road on it and nothing's broken
except the rear brake cable (easy fix).

So I'm thinking it's time for an upgrade ;-)

On the wish list are Shimano or similar quality gears, full suspension,
no need for disc brakes as far as i can see, decent saddle. Budget of
200-250ish. I've seen things like Saracen AWOLs for about that new on
ebay.

Something lighter would be nice too, I'm fed up half killing myself
lifting it over fences and padlocked gates!

1) Why do some people prefer hardtails for offroad use? I can see how
pedalling might be a bit more efficient but it must be very
uncomfortable (lot of rough tracks up here).

2) I'm assuming the only real bonus with disc brakes is wet weather
performance. My current bikes brakes are excellent, better than my 600
quid tourer's in fact!

3) Anything else that should be on my wish list? I'm fairly new to the
mountain bike game.

4) Any specific recommendations?

--
Who needs a life when you've got Unix? :-)
Email: [email hidden], John G.Burns B.Eng, Bonny Scotland
Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage!
Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html
www.Strathspey.co.uk - Quality Binoculars at a Sensible price

sorry, I meant 'Prices'... siffering from fat finger syndrome...

"John Burns" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Until last year I was always an on-road man, tried to do 100 miles a
week but didn't always manage :-)

Then last Jan I got a cheap "Boss" mountian bike from ebay, unwanted
Christmas present at a bargain price. Just to see if I liked off
roading, I do :-) It's a 15 speed (too slow on road by far), full
suspension, awful saddle, dodgy gear change, but it did the job. I
currently do about 50+ miles a week off road on it and nothing's broken
except the rear brake cable (easy fix).

So I'm thinking it's time for an upgrade ;-)

On the wish list are Shimano or similar quality gears, full suspension,
no need for disc brakes as far as i can see, decent saddle. Budget of
200-250ish. I've seen things like Saracen AWOLs for about that new on
ebay.

Something lighter would be nice too, I'm fed up half killing myself
lifting it over fences and padlocked gates!

1) Why do some people prefer hardtails for offroad use? I can see how
pedalling might be a bit more efficient but it must be very
uncomfortable (lot of rough tracks up here).

2) I'm assuming the only real bonus with disc brakes is wet weather
performance. My current bikes brakes are excellent, better than my 600
quid tourer's in fact!

3) Anything else that should be on my wish list? I'm fairly new to the
mountain bike game.

4) Any specific recommendations?

--
Who needs a life when you've got Unix? :-)
Email: [email hidden], John G.Burns B.Eng, Bonny Scotland
Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage!
Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html
www.Strathspey.co.uk - Quality Binoculars at a Sensible price

"John Burns" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Until last year I was always an on-road man, tried to do 100 miles a
week but didn't always manage :-)

Then last Jan I got a cheap "Boss" mountian bike from ebay, unwanted
Christmas present at a bargain price. Just to see if I liked off
roading, I do :-) It's a 15 speed (too slow on road by far), full
suspension, awful saddle, dodgy gear change, but it did the job. I
currently do about 50+ miles a week off road on it and nothing's broken
except the rear brake cable (easy fix).

So I'm thinking it's time for an upgrade ;-)

On the wish list are Shimano or similar quality gears, full suspension,
no need for disc brakes as far as i can see, decent saddle. Budget of
200-250ish. I've seen things like Saracen AWOLs for about that new on
ebay.

You cannot get good front suspension at £250, never mind full suspension.
I'd go for a steel hardtail (a quality one, not one that's steel because
steel's cheaper than Alloy) if you can stretch to it. Slightly comfier than
alu and not too dear. But I would say that, because I ride one myself. OTOH,
fit bigger tyres, and you'll be comfy for a lot less $.

Quoted message said:

Something lighter would be nice too, I'm fed up half killing myself
lifting it over fences and padlocked gates!

1) Why do some people prefer hardtails for offroad use? I can see how
pedalling might be a bit more efficient but it must be very
uncomfortable (lot of rough tracks up here).

Lots lighter, lots cheaper, lots simpler. I can keep up with a mate on his
full suspension bike down the hills, if not up them, so what's the point in
going full suspension? My bike cost £600 to buy and add the bits I wanted to
(Marzocchis and disk brakes), and I've not had to replace any bits and bobs
yet.

Quoted message said:

2) I'm assuming the only real bonus with disc brakes is wet weather
performance. My current bikes brakes are excellent, better than my 600
quid tourer's in fact!

As others have said, sensitivity is a lot better with disks, but IMO a well
set up pair of parallel push V brakes will stop you just as fast and with
pretty good sensitivity too.

Quoted message said:

3) Anything else that should be on my wish list? I'm fairly new to the
mountain bike game.

Deore parts, decent tyres, decent brakes, aheadset. As decent a frame as you
can get (at least 1 1/8 headtube so you can swap forks).

Quoted message said:

4) Any specific recommendations?

Get a second hand pair of Marzocchis when your forks stop working, a cheap
alloy or half decent steel hardtail (the only ones you'll see around £300
second hand will be inbreds and a few Konas IIRC). Make sure you have decent
tyres on the bike and you won't go far wrong.

"Mister Bartlett" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Simon Brooke said:

Cheap rear suspension and cable operated disk
brakes count as gimmicks.

Most people would disagree with you as far as cable disks are concerned.
A good set of cable disk brakes is as good as a hydraulic set, and a lot
less trouble. They have the same advantages, good performance in water
and mud, excellent stopping power etc., and the added advantage that you
don't have to mess with hydraulic fluid.

Oh really?
As I've posted elsewhere I've had Hope Mini Monos for 2 years now and apart
from replacing worn pads, an operation simpler than replacing rim brake
pads, have had no trouble, how's it possible to have less than none?
And no-one is going to sell me the idea that an elastic cable dragging
through tubes and guides is as smooth as a non-compressible fluid medium
when in good repair, inject abit of trail muck into the tubes and guides
and things get worse. This is why hydraulic brakes are more sensitive.
And finally.....if cables are superior how come they were dropped long ago
by car makers across the full spectrum of vehicles?
--
Pete
http:[email hidden]/Stuff

in message <[email hidden]>, Mister Bartlett

(') said:

Simon Brooke said:

Cheap rear suspension and cable operated disk
brakes count as gimmicks.

Most people would disagree with you as far as cable disks are
concerned. A good set of cable disk brakes is as good as a hydraulic
set, and a lot less trouble. They have the same advantages, good
performance in water and mud, excellent stopping power etc., and the
added advantage that you don't have to mess with hydraulic fluid.

No, they don't have the same advantages. Even the best disk brake is not
as good in terms of sheer stopping power as the best rim brake - a rim
is, after all, equivalent to a 25" disk. The advantage of hydraulic
brakes (whether rim or disk) is sensitivity and control, and frankly any
hydraulic brake (rim or disk) is better than any cable operated brake
(rim or disk).

In exceptionally muddy conditions I'd agree disks are better because it's
hard to keep the brake tracks on a rim brake free of mud, but if your
brakes aren't working well in the wet fix 'em.

It's worth pointing out that in serious competition, most of the lighter
riders (including Gunne Rita Dahle, who's won the womens' XC world cup
so often it's boring) use V brakes, not disks (some of the top men do,
too). V brakes have real benefits over disks - they're lighter, they
don't put torsional strain on the wheel so it can be lighter, the hub
can be wider so the wheel can be stronger (or, again, lighter), and
because the leverage is much better the pad pressure required to achieve
the same braking force is much less. Only the sensitivity benefits of
hydraulic disks allow them to be competitive with lighter, more powerful
V brakes. I've never seen cable operated disks on any bike ridden at
international level. If they worked, they'd be used.

Quoted message said:

I recommend that the OP head over to the forum at
www.singletrackworld.com and ask his quetsion there.

I'd agree with that.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Morning had broken. I found a rather battered tube of Araldite
resin in the bottom of the toolbag.

Peter B said:

"Mister Bartlett" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Simon Brooke said:

Cheap rear suspension and cable operated disk
brakes count as gimmicks.

Most people would disagree with you as far as cable disks are concerned.
A good set of cable disk brakes is as good as a hydraulic set, and a lot
less trouble. They have the same advantages, good performance in water
and mud, excellent stopping power etc., and the added advantage that you
don't have to mess with hydraulic fluid.

Oh really?
As I've posted elsewhere I've had Hope Mini Monos for 2 years now and apart
from replacing worn pads, an operation simpler than replacing rim brake
pads, have had no trouble, how's it possible to have less than none?
And no-one is going to sell me the idea that an elastic cable dragging
through tubes and guides is as smooth as a non-compressible fluid medium
when in good repair, inject abit of trail muck into the tubes and guides
and things get worse. This is why hydraulic brakes are more sensitive.
And finally.....if cables are superior how come they were dropped long ago
by car makers across the full spectrum of vehicles?

I don't think I said they were superior - I said that they have the
advantage of not needing hydraulic fluid. A lot of Hope Mini users -
myself included - find that they require regular adjustment, bleeding
and cleaning in order to retain their efficiency.

I agree that they're more sensitive and powerful. However, I also
believe the people who tell me that, having compared hydraulic brakes
with, say, Avid cable brakes, the Avids are a very good alternative.

And your comment about car brakes is irrelevant - the operating
environment is quite different.

Mr B;

--
Encrypted e-mail address. Click to mail me:
<http://cerbermail.com/?nKYh3qN4YG>

..

Quoted message said:

4) Any specific recommendations?

Reference my previous post.

There are loads of second hand Marins on eBay - doubtless there are loads of
Orange, GT etc.

Well worth a look.

John

in message <[email hidden]>, R. Murphy

(') said:

"John Burns" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On the wish list are Shimano or similar quality gears, full
suspension, no need for disc brakes as far as i can see, decent
saddle. Budget of 200-250ish. I've seen things like Saracen AWOLs for
about that new on ebay.

To be honest, for this price I do not think you will be getting much
quality. Up your budget to about 700 - 900 - or perhaps even a tad
higher - and have a look at the offerings by Marin, Specilaised, Muddy
Fox, Scott etc. Its probably best to avoid complicated linkages and, in
my view, find something with a "proper" downtube such as the Marins
have, rather than something where the seat post fouls the suspension if
you drop the seat.

While I'd generally agree with the comment about complicated linkages, if
you've got £900 to spend on a mountain bike have a test ride on a Giant
Trance 4. You get a lot of bike for your money - it's the cheapest full
suspension bike I would rate as value for money. Yes, there are a lot of
bushes, but the position of the suspension unit in front of the seatpost
protects it from mud, which the Scotts and Specializeds suffer from
badly. Britain's a lot muddier than California.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Age equals angst multiplied by the speed of fright squared.
;; the Worlock

"Mister Bartlett" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I don't think I said they were superior - I said that they have the
advantage of not needing hydraulic fluid. A lot of Hope Mini users -
myself included - find that they require regular adjustment, bleeding
and cleaning in order to retain their efficiency.

Oops, yes, I've re-read your reply to Simon and got down off my high horse
:-)
Simon implied cable discs were gimmicks and you've said a lot of people
would disagree but you never said they were superior, my mistake, sorry.
My own personal findings however are that my Hope Mono Minis have required
less fettling than the cantis and vees I've previously used in anger on mtbs
(let's Hope I'm not tempting fate :-)
--
Pete
http:[email hidden]/Stuff

Simon Brooke said:

No, they don't have the same advantages. Even the best disk brake is not
as good in terms of sheer stopping power as the best rim brake - a rim
is, after all, equivalent to a 25" disk. The advantage of hydraulic
brakes (whether rim or disk) is sensitivity and control, and frankly any
hydraulic brake (rim or disk) is better than any cable operated brake
(rim or disk).

If the rim could be built and kept as true as a disk that might be true
but they can't.

--
Tony

"The best way I know of to win an argument is to start by being in the
right."
- Lord Hailsham

Quoted message said:

Lots lighter, lots cheaper, lots simpler. I can keep up with a mate on his
full suspension bike down the hills, if not up them, so what's the point in
going full suspension?

Why does full suspension make you faster uphill? Or is he fitter than
you? :-)

--
Who needs a life when you've got Unix? :-)
Email: [email hidden], John G.Burns B.Eng, Bonny Scotland
Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage!
Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html
www.Strathspey.co.uk - Quality Binoculars at a Sensible price

Tony Raven said:

If the rim could be built and kept as true as a disk that might be true
but they can't.

Jobst Brandt for you on line 2.

In a previous life I designed brakes at Girling. Disks most certainly can
warp [1], and the sorting out thereof can be difficult.

[1] Albeit in a different way to wheel rims.

Mike