Is this practical

Jinx said:

I've just bought a 'new' secondhand bike (Cannondale badboy), via ebay, and
although it's a nice machine, the very narrow tyres keep 'grounding' on bumps
and bad surfaces - particularly the back.

(By grounding, I mean that it feels as if the rim actually hits the road through
the tyre).

I can't believe that the wheels and tyres will last very long if I keep riding
it like this. (I'm 6' 3" and 17 stone, so quite heavy).

What I was thinking of doing was putting a wider tyre on the back so that it's
got a bit more air to keep the rim off the rubber.

Is it OK to have a different width tyre at the back? Would 32mm be a sensible
compromise?

Get a pump with a pressuregauage, the max pressure is printed somewhere
on the sidewall of the tires. Inflate before every ride.
--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

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

Quoted message said:

I've just bought a 'new' secondhand bike (Cannondale badboy), via ebay,
and
although it's a nice machine, the very narrow tyres keep 'grounding' on
bumps
and bad surfaces - particularly the back.

(By grounding, I mean that it feels as if the rim actually hits the road
through
the tyre).

I can't believe that the wheels and tyres will last very long if I keep
riding
it like this. (I'm 6' 3" and 17 stone, so quite heavy).

What I was thinking of doing was putting a wider tyre on the back so that
it's
got a bit more air to keep the rim off the rubber.

Is it OK to have a different width tyre at the back? Would 32mm be a
sensible
compromise?

I'm sure the badboy could take a 32mm tyre, but, although it may seem
obvious, are you sure they're properly inflated? A 25mm tyre generally
requires and takes a higher pressure than an narrower one - mine will go to
115psi. Bear in mind as well that if you're used to wider tyres, the ride
is going to feel much harder if you do have a properly inflated narrow tyre.

Rich

Jinx said:

I've just bought a 'new' secondhand bike (Cannondale badboy), via
ebay, and although it's a nice machine, the very narrow tyres keep
'grounding' on bumps and bad surfaces - particularly the back.

(By grounding, I mean that it feels as if the rim actually hits the
road through the tyre).

I can't believe that the wheels and tyres will last very long if I
keep riding it like this. (I'm 6' 3" and 17 stone, so quite heavy).

What I was thinking of doing was putting a wider tyre on the back so
that it's got a bit more air to keep the rim off the rubber.

Is it OK to have a different width tyre at the back? Would 32mm be a
sensible compromise?

Sounds like the tyres are not pumped up hard enough for your weight. If it
really is grounding, you'll get pinch-flats very quickly.

Sheldon Brown (as ever) has some suggested starting points for playing with
tyre pressures.
http://sheldonbrown.com/tyres.html#pressure
Extrapolating Sheldon's suggestions, assuming 50-50 weight distribution
(under-estimate of rear weight), you should be looking for at least 120psi
into a 28mm tyre.

A 32mm rear might be better, and I can't think of a reason why you can't use
different sizes. However, play with pressures first.

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

On 07/03/2005 10:57:27 'Richard Goodman said:

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

Quoted message said:

Quoted message said:

I've just bought a 'new' secondhand bike (Cannondale badboy), via ebay,
and although it's a nice machine, the very narrow tyres keep 'grounding'
on bumps and bad surfaces - particularly the back.

Quoted message said:

Quoted message said:

(By grounding, I mean that it feels as if the rim actually hits the road
through the tyre).

Quoted message said:

Quoted message said:

I can't believe that the wheels and tyres will last very long if I keep
riding it like this. (I'm 6' 3" and 17 stone, so quite heavy).

Quoted message said:

Quoted message said:

What I was thinking of doing was putting a wider tyre on the back so that
it's got a bit more air to keep the rim off the rubber.

Quoted message said:

Quoted message said:

Is it OK to have a different width tyre at the back? Would 32mm be a
sensible compromise?

Quoted message said:

I'm sure the badboy could take a 32mm tyre, but, although it may seem
obvious, are you sure they're properly inflated? A 25mm tyre generally
requires and takes a higher pressure than an narrower one - mine will go
to 115psi. Bear in mind as well that if you're used to wider tyres, the
ride is going to feel much harder if you do have a properly inflated
narrow tyre.

Quoted message said:

Rich

If you do go for a fatter tyre, check it will clear the frame, I
recommend the Schwalbe Big Apple tyre by the way, good comfort, tough
and rolls well.
--

Buck

I would rather be out on my Catrike

http://www.catrike.co.uk

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

Quoted message said:

I've just bought a 'new' secondhand bike (Cannondale badboy), via ebay,

and

Quoted message said:

although it's a nice machine, the very narrow tyres keep 'grounding' on

bumps

Quoted message said:

and bad surfaces - particularly the back.

(By grounding, I mean that it feels as if the rim actually hits the road

through

Quoted message said:

the tyre).

I can't believe that the wheels and tyres will last very long if I keep

riding

Quoted message said:

it like this. (I'm 6' 3" and 17 stone, so quite heavy).

What I was thinking of doing was putting a wider tyre on the back so that

it's

Quoted message said:

got a bit more air to keep the rim off the rubber.

Is it OK to have a different width tyre at the back? Would 32mm be a

sensible

Quoted message said:

compromise?

I weigh about the same and have found that *narrow* (23 and 25 mm) tyres
have to be pumped very hard if I am not to get snakebite punctures -- a
classic symptom of *grounding* the tyre.

Moving to wider gives a bit more bounce and is less susseptable to
snakebites -- though they are still best pumped fairly hard.

If you are not actually puncturing at the moment why not bank in some more
air -- say 100 psi for 25 mm or 110+ for 23 mm and see what happens.

T

Quoted message said:

I've just bought a 'new' secondhand bike (Cannondale badboy), via ebay, and
although it's a nice machine, the very narrow tyres keep 'grounding' on bumps
and bad surfaces - particularly the back.

(By grounding, I mean that it feels as if the rim actually hits the road through
the tyre).

I wonder if you're running a high enough rear tyre pressure? I run my
mountian bike tyres about 2.5 bar.

--
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

"Richard Goodman" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I'm sure the badboy could take a 32mm tyre, but, although it may seem
obvious, are you sure they're properly inflated? A 25mm tyre generally
requires and takes a higher pressure than an narrower one - mine will go

to

Quoted message said:

115psi.

My thoughts exactly.
Bear in mind a poor handpump will not achieve that pressure and a good one
often only with hard work. A good high pressure track pump would be a good
investment, don't go a for a fatter barrelled one, they are more biased to
getting a lot of low pressure air in quickly.

In fact it's time I got off me bum to pump up me tyres and go....

Pete

Jinx said:

I can't believe that the wheels and tyres will last very long if I keep riding
it like this. (I'm 6' 3" and 17 stone, so quite heavy).

I'm currently using 32mm Michelin Transworld City tyres on my tourer.
I,m 15 - Ok 15 and a bit stone, and find 80 psi in the back and 60 psi
in the front works well.
These tyres are cheap (£10 each) but feel like they roll just as
well as the Conti Top Touring tyres previously fitted. My commuter bike
has a Transworld City tyre on the back and it's not punctured in a
couple of thousand miles commuting.
Iain

Buck said:

If you do go for a fatter tyre, check it will clear the frame

....with a bit to spare, to allow for a slightly out-of-true wheel, at
least.

~PB

Simon Brooke said:

No, they won't; indeed you've probably wrecked them already.

Well, that's nice.

Thanks to all those who have responded.

When I picked up the bike, the person I bought it from assured me that the tyres
were correctly inflated (and for me, that means (well, meant) fully inflated).

I now realise that they are somewhat underinflated for someone of my size - I
had a good read of what Sheldon Brown had to say on the subject.

Although a hand pump and seperate pressure gauge were adequate for my last bike,
I clearly need a track pump with a good quality gauge for this one, and I've
ordered one from wiggle. Just a shame I can't use the bike again until it
arrives.

I'm rather glad that it's the pressure rather than the tyres, as the narrow ones
look really nice, and I've never been that concerned about the harsher ride you
get with higher pressure.

Also, it means that the bike will be even faster once the tyres have been
inflated some more, and it seems something of a flyer already (at least compared
with my old, no name MTB).

Just hoping that I haven't done any damage to the wheels. At least they're still
round, and have no broken spokes.

in message <[email hidden]>, Jinx

(') said:

On Sun, 03 Jul 2005 20:08:43 +0100, Simon Brooke <[email hidden]>

Quoted message said:

No, they won't; indeed you've probably wrecked them already.

Well, that's nice.

Just hoping that I haven't done any damage to the wheels. At least
they're still round, and have no broken spokes.

The issue is potential damage to the rims, which is what you can get if
you ride on under-inflated tyres. I would inspect them fairly carefully;
if there are any obvious nicks or flat spots on the edges of the rims,
my advice would be to carefully file them smooth, and you'll probably
get away with it. I've done this in the past and it has worked for me.
However if anyone else posts in response to this that this is a bad
idea, they may well be right.

Sharp bits on rims will lead to punctures. Nicks in rims will often lead
to poor braking performance.

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

Tony Blair's epitaph, #1: Tony Blair lies here.
Tony Blair's epitaph, #2: Trust me.

Simon Brooke said:

in message <[email hidden]>, Jinx

(') said:

On Sun, 03 Jul 2005 20:08:43 +0100, Simon Brooke <[email hidden]>

Quoted message said:

No, they won't; indeed you've probably wrecked them already.

Well, that's nice.

Just hoping that I haven't done any damage to the wheels. At least
they're still round, and have no broken spokes.

The issue is potential damage to the rims, which is what you can get if
you ride on under-inflated tyres. I would inspect them fairly carefully;
if there are any obvious nicks or flat spots on the edges of the rims,
my advice would be to carefully file them smooth, and you'll probably
get away with it. I've done this in the past and it has worked for me.
However if anyone else posts in response to this that this is a bad
idea, they may well be right.

Sharp bits on rims will lead to punctures. Nicks in rims will often lead
to poor braking performance.

I checked the rims VERY carefully, and there are no nicks, sharp bits, or flats,
so I hope I'm going to be OK.

I only did about 12 miles on the bike, and the vast majority of that was without
any incident.

Just to say thanks to all those who responded.

I got a track pump from Wiggle (ordered Sunday, delivered this morning), and
discovered that the tyres were only inflated to 40psi (They still felt quite
hard to me being used to that sort of pressure on the MTB).

However, talk of 110 and 120psi is a little wide of the mark, as the tyres are
only rated up to 90psi.

I pumped them up to 80, and the grounding problems disappeared. Quite a firm
ride, but I'm not too bothered about that.

Bike is even faster now. I hope my heart can handle it as it seems to DEMAND
that it be ridden as fast as possible.

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

Quoted message said:

Just to say thanks to all those who responded.

I got a track pump from Wiggle (ordered Sunday, delivered this morning),

and

Quoted message said:

discovered that the tyres were only inflated to 40psi (They still felt

quite

Quoted message said:

hard to me being used to that sort of pressure on the MTB).

However, talk of 110 and 120psi is a little wide of the mark, as the tyres

are

Quoted message said:

only rated up to 90psi.

I pumped them up to 80, and the grounding problems disappeared. Quite a

firm

Quoted message said:

ride, but I'm not too bothered about that.

40 psi is on the low side for someone of your weight on an mtb, comfortable
maybe but a high risk of pinch punctures.
80psi isn't high either but if your're happy and no more punctures that's
all that matters.

Quoted message said:

Bike is even faster now. I hope my heart can handle it as it seems to

DEMAND

Quoted message said:

that it be ridden as fast as possible.

Hehe. Isn't that the problem with a nice road bike, they just feel happier
at speed ;-)

--
Pete
http:[email hidden]/P

On Tue, 5 Jul 2005 16:39:26 +0000 (UTC), "Peter B" <[email hidden]>

Quoted message said:

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

Quoted message said:

40 psi is on the low side for someone of your weight on an mtb, comfortable
maybe but a high risk of pinch punctures.

Having just checked them with the gauge on the new pump, I find that they (MTB)
were actually at around 60 psi.

That explains why when I inflated them to read 60 on the old gauge, they came
off the rim - not pleasant.

They were nice and hard although not the rock hard that the narrow ones are!

Quoted message said:

80psi isn't high either but if your're happy and no more punctures that's
all that matters.

The tyres are only rated to 90. I'd be happy to go to 90, but I really, really
don't want them coming off the rim. (Is that less likely with narrow tyres?)

Not sure why these are rated so low when everyone was talking about 100 - 120
psi.

One other question.

How on earth do you pump these up if you have to change the tube whilst cycling?
Even with my weight, I really have to lean on the track pump to get 80psi. I
can't believe that a hand pump would give you that pressure, and certainly not
120psi. So what do you do when on the road? (The track pump is WAY too big to
take along).

On 07/05/2005 17:54:06 (Jinx) said:

One other question.

Quoted message said:

How on earth do you pump these up if you have to change the tube whilst
cycling? Even with my weight, I really have to lean on the track pump to
get 80psi. I can't believe that a hand pump would give you that pressure,
and certainly not 120psi. So what do you do when on the road? (The track
pump is WAY too big to take along).

You get a dual piston hand pump. Or one of those new compact foot pumps.

--

Buck

I would rather be out on my Catrike

http://www.catrike.co.uk

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

Quoted message said:

How on earth do you pump these up if you have to change the tube whilst

cycling?

Quoted message said:

Even with my weight, I really have to lean on the track pump to get 80psi.

I

Quoted message said:

can't believe that a hand pump would give you that pressure, and certainly

not

Quoted message said:

120psi. So what do you do when on the road? (The track pump is WAY too big

to

Quoted message said:

take along).

Maybe I'm particularly fortunate <1> but I've had very few punctures on my
road bikes in 10's of thousands of miles. When I do I just accept that I'm
going to be on underinflated tyres for the remainder of the ride and am
more picky about road surfaces.
<1> This can be a problem. The last time, which is perhaps 2 years ago, I
had a puncture on the shiney bike I found the tube was falling apart, no
worries, I carry two spares anyway. Unfortunately the valve fell apart on
one and t'other had a bad case of saddle-pack rash. I used all my patches to
get one servicable tube, needless to say I took the shortest route home.
If you suffer regular punctures, like my mtb when used on bridleways, you
tend to rotate your innertube stock and are usually aware of how many
patches you have and whether the glue's solidified in the tube :-)
--
Pete
http:[email hidden]/P

in message <[email hidden]>, Jinx

(') said:

Peter B said:

80psi isn't high either but if your're happy and no more punctures
that's all that matters.

The tyres are only rated to 90. I'd be happy to go to 90, but I really,
really don't want them coming off the rim. (Is that less likely with
narrow tyres?)

Not sure why these are rated so low when everyone was talking about 100
- 120 psi.

One other question.

How on earth do you pump these up if you have to change the tube whilst
cycling? Even with my weight, I really have to lean on the track pump
to get 80psi. I can't believe that a hand pump would give you that
pressure, and certainly not 120psi. So what do you do when on the road?
(The track pump is WAY too big to take along).

Smaller-diameter barrelled pumps are generally easier to pump to higher
pressures. I use Blackburn Airsticks on all my bikes - they're small,
light and neat and will easily to pump to 120psi (although it takes a
lot of strokes). Another pump that gets recommended a lot is the Topeak
Road Morph, which is bigger, and works like a track pump, but can easily
be carried on the bike.

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

;; Semper in faecibus sumus, sole profundum variat.

Jinx said:

The tyres are only rated to 90. I'd be happy to go to 90, but I
really, really don't want them coming off the rim.

From http://www.sheldonbrown.com/tyres.html#pressure :

"The legal department wants the number kept conservatively low, in
case the tyre gets mounted on a defective or otherwise loose fitting rim.
They commonly shoot for half of the real blow-off pressure.

"The marketing department wants the number high, because many tyre
purchasers make the (unreliable) assumption that the higher the pressure
rating, the better the quality of the tyre.

"Newbies often take these arbitrary ratings as if they had some
scientific basis. While you'll rarely get in trouble with this approach,
you will usually not be getting the best possible performance with this
rote approach.

"Savvy cyclists experiment with different pressures, and often even
vary the pressure for different surface conditions.

"Optimal pressure for any given tyre will depend on the load it is
being asked to support. Thus, A HEAVIER RIDER NEEDS A HIGHER PRESSURE than
a lighter rider, for identical tyres."

Also don't forget that rear tyres carry more weight than front tyres, so
require greater pressure.

Quoted message said:

(Is that less likely with narrow tyres?)

No, but you can test by over-inflating and leaving to stand, ie. inflating
to a higher pressure than you would ever use. If the tyre stays on with
higher than normal pressure for 18 hours then it's bound to be fine at
usual pressure fo rgood. Be prepared to loose an inner tube in a failed
test.

Quoted message said:

Not sure why these are rated so low when everyone was talking about
100 - 120 psi.

The tyres may be of a lower quality (in terms of performance) or just are
a bit wider. On the other hand, the quality & width may be the same but
the manufacturer has a different idea about what pressure to recommend.

Quoted message said:

One other question.

How on earth do you pump these up if you have to change the tube
whilst cycling? Even with my weight, I really have to lean on the
track pump to get 80psi. I can't believe that a hand pump would give
you that pressure, and certainly not 120psi. So what do you do when
on the road? (The track pump is WAY too big to take along).

You get a *good* pump such as Zefal/Truflo HPX (full-length pump) --
search Google Groups for tips on how to attach this under the bike's top
tube. 120 psi is then not impossible with average arm-strength. If a
mini pump is essential, the Topeak Pocket Rocket can also manage very high
pressures, although it takes ages to get there because the barrel is so
small. A CO2 inflator is another way.

By the way, a really decent track pump (eg. Silca Super Pista) will need
little effort to manage 120psi and beyond.

~PB