Tire size help

Ed in Waxhaw said:

I've got a trek 7700 hybrid that came stock with Bontrager 700x 35C tires. I
just replaced them with Conti Ultimate 2000 tires sized 700 x 25C. I called
Trek and they recommended that I not use them. Can you guys give me some
real life answers as to whether or not I'm setting myself up for disaster?
Also I'm about 250lbs. putting about 125 miles a week on the bike.

Not "disaster" but possibly a flat tire. A person your weight on tires
that skinny needs to keep them pumped up VERY hard to avoid pinch flats
due to road hazards. As a result, you can expect the ride to be very
harsh.

If the harsh ride doesn't bother you, and the roads you ride on are
smooth enough, no reason not to stick with them.

If you find you are getting a lot of flats, it indicates you probably
should go to something wider, but in the abscence of a problem there's
no reason not to keep on riding the 25s. Just make sure to keep the
pressure topped up regularly.

Sheldon "High Pressure" Brown
+--------------------------------------------------------+
| There is no conclusive evidence of life after death. |
| But there is no evidence of any sort against it. |
| Soon enough you will know, so why fret about it? |
| --Robert A. Heinlein |
+--------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Ramprat said:

Hi,
I've got a trek 7700 hybrid that came stock with Bontrager 700x 35C tires. I
just replaced them with Conti Ultimate 2000 tires sized 700 x 25C. I called
Trek and they recommended that I not use them. Can you guys give me some
real life answers as to whether or not I'm setting myself up for disaster?
Also I'm about 250lbs. putting about 125 miles a week on the bike.
Thanks,

Ed in Waxhaw

There isn't a hard and fast rule, and both rims and tires
vary greatly by manufacturer's interpretation of size ( some
700-28 are smaller than other brands of 700-23).
That being said, you want the tire to amply hang over the
rim. You'll normally need to release your brake to get a
wheel out if the tire is appropriately proportional to the
rim ( unless you leave your brakes fairly loose. I'm sure
someone will write that they can drop a wheel without
undoing the brake release and in fact most of my bikes could
with tubulars on standard rims but he has a hybrid and my
general point is directed to him)

So I guess without knowing the rim I can't kibitz but you
might ride past your dealer and ask if the tires you've
mounted are going to work well with the rims you have.

If you selected too narrow a tire, the risk is that you'll
pinch the tube easily on impact and possibly even dent a rim
on a normal pavement anomaly.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Ramprat' [email protected] said:

just replaced them with Conti Ultimate 2000 tires sized 700 x 25C. I called

Do you mean Conti Ultra 2000? I googled and found nada for Ultimate.

Quoted message said:

Trek and they recommended that I not use them. Can you guys give me some
real life answers as to whether or not I'm setting myself up for disaster?
Also I'm about 250lbs. putting about 125 miles a week on the bike.

I have a 20mm front and 23mm rear. I weigh 210, but carry lots of
water (up to 128oz) and all sorts of crud on my rear rack. I do fine
with those tires, with the rear at 120 psi. You ought to be okay as
long as you inflate to max pressure (120 for Ultra 2000). Recently I
put on a tire that takes 145 psi, and am fine at that also.
--
Rick Onanian

"Rick Onanian" <[email hidden]> wrote

Quoted message said:

I have a 20mm front and 23mm rear. I weigh 210, but carry lots of
water (up to 128oz) and all sorts of crud on my rear rack.

Yikes, nobody around here runs 20 mm, not even the racer-boys. You must have
perfect pavement.

They are the Ultra tires. I just took them out for a 35 mile ride carrying a
3 litre camelbak. The pavement was mostly smooth with no major potholes but,
lots of construction areas. My average speed increased about 3mph and my
anxiety about these tires is starting to fade
"Peter Cole" <[email hidden]> wrote in message
news:yESJc.104995$XM6.26797@attbi_s53...

Quoted message said:

"Rick Onanian" <[email hidden]> wrote

Quoted message said:

I have a 20mm front and 23mm rear. I weigh 210, but carry lots of
water (up to 128oz) and all sorts of crud on my rear rack.

Yikes, nobody around here runs 20 mm, not even the racer-boys. You must

have

Quoted message said:

perfect pavement.

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

Quoted message said:

They are the Ultra tires. I just took them out for a 35 mile ride carrying a
3 litre camelbak. The pavement was mostly smooth with no major potholes but,
lots of construction areas. My average speed increased about 3mph and my
anxiety about these tires is starting to fade
"Peter Cole" <[email hidden]> wrote in message
news:yESJc.104995$XM6.26797@attbi_s53...

Quoted message said:

"Rick Onanian" <[email hidden]> wrote

Quoted message said:

I have a 20mm front and 23mm rear. I weigh 210, but carry lots of
water (up to 128oz) and all sorts of crud on my rear rack.

Yikes, nobody around here runs 20 mm, not even the racer-boys. You must

have

Quoted message said:

perfect pavement.

25 mm should be fine, I was yikes'ing over 20 mm -- that's a huge difference.
When you're a big rider, you have to think of tires as rim protectors, pinch
flats are a nuisance, but trashed rims gets expensive.

Peter Cole said:

"Rick Onanian" <[email hidden]> wrote

Quoted message said:

I have a 20mm front and 23mm rear. I weigh 210, but carry lots of
water (up to 128oz) and all sorts of crud on my rear rack.

Yikes, nobody around here runs 20 mm, not even the racer-boys. You must have
perfect pavement.

No, I just inflate it well (110 psi). A 20mm rear might not work for
me, but it's okay in the front. Not only is my pavement average (at
best), but I've even done some off-road riding with it recently on
unfinished bike paths; probably 20 or 30 miles in the past few
weeks. It's rather difficult once the dirt gets soft... 😉

I snakebit the 145psi 23mm rear while off-road last Saturday, when
there was suddenly a sharp-edged rectangular piece of concrete
sticking out (about 1" high) of the hardpack dirt, conveniently the
same exact color as the dirt. I reacted in time to get the front
over it but didn't unweight the rear quickly enough.
--
Rick Onanian