Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

"The 33"-Road Bike Racing We set this forum up for our members to discuss their experiences in either pro or amateur racing, whether they are the big races, or even the small backyard races. Don't forget to update all the members with your own race results.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 04-12-14, 06:02 PM   #1
gruntle
Junior Member
Thread Starter
 
Join Date: Mar 2012
Location: Seattle
Bikes:
Posts: 23
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Will a wide rim allow me to run 25mm tire without rubbing my frame?

I have plenty of clearance on the front to run whatever size tire I want but the rear is another story.

A while back I mounted a 25mm tire to my 19mm rim and it rubbed the frame. I had room on the sides of the tire but the tire contacted the at the middle of the tread.
I'v been stuck with 23mm tires but I'm getting ready to replace my wheels and am looking at my rim options right now.
I'm wondering if I mounted a 25mm tire to a wide 23mm rim would this reduce the height of the tire? I figure the side walls are being spread out so it seems like the tires total height would be reduced.

The 25mm tire that rubbed was a Conti 4000s.

Thanks.

Last edited by gruntle; 04-12-14 at 06:05 PM.
gruntle is offline   Reply With Quote
Old 04-12-14, 07:16 PM   #2
tetonrider
Senior Member
 
Join Date: Aug 2007
Bikes:
Posts: 3,290
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
i'm assuming you're talking clincher tires here.

in my experience, continental gp4000s tend to run a little tall for the size (which is why some tout there aerodynamics).

a wider rim will generally make tires sit a bit lower. if you think about it, there is a fix amount of material, and if the beads are stretched further apart (due to the wider rim), then there is less material to extend up above the rim. the difference is likely small, but it may be just what you need.

if your clearance is that tight, i'd give a minute to think about any debris getting caught and potentially damaging the frame and/or locking the wheel.

if you're talking tubulars, the design means that the tire's dimensions (which can be different from what is quoted) reflect the diameter of a cross-section -- height or width. the width and height won't really change based on the width of the rim. for a clinker, things are a bit more variable.
tetonrider is offline   Reply With Quote
Old 04-12-14, 08:04 PM   #3
prathmann
Senior Member
 
Join Date: Nov 2008
Location: Bay Area, Calif.
Bikes:
Posts: 5,951
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Quote:
Originally Posted by tetonrider View Post
a wider rim will generally make tires sit a bit lower.
Only once the rim gets *really* wide. Consider starting with a tire that measures 25*pi mm from bead to bead when laid flat. Mount that on a *very* narrow rim with just a few mm between the sides so the tire forms a circular cross-section with a diameter of 25mm above the rim. So it's 25mm wide and also has a high point 25 mm above the rim. Now replace that rim with one that's 50 mm wide. The circumference of the tire is still 25*pi mm, but now the tire forms a semi-circular cross-section with a radius of 25mm, so it's 50 mm wide but still extends 25 mm above the rim (circum. of a semi-circle = pi * r). So going from a rim of almost zero width to one that's 50mm wide hasn't gained you anything in terms of vertical clearance.

Now if you continue to widen the rim the tire will finally start to have a high point closer to the rim - in the extreme case you end up with a rim that's 25* pi mm wide and a tire that lies completely flat across that rim (good luck getting it to seat properly - and of course you'd be riding more on the rim that on the tire).
prathmann is offline   Reply With Quote
Old 04-12-14, 08:17 PM   #4
mollusk
Elite Fred
 
mollusk's Avatar
 
Join Date: Aug 2005
Location: Edge City
Bikes: 2009 Spooky (cracked frame), 2006 Curtlo, 2002 Lemond (current race bike) Zurich, 1987 Serotta Colorado, 1986 Cannondale for commuting, a 1984 Cannondale on loan to my son
Posts: 10,754
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
My race wheels are "aero" by being significantly wider than my normal training wheels so that there is no sudden change in profile. I didn't have any problems with frame clearance, but I did need to purchase special low profile pad holders for my brakes. It was either that or trimming off a lot of the brake pads for my race brake pads.
mollusk is offline   Reply With Quote
Old 04-13-14, 07:23 AM   #5
shovelhd 
Senior Member
 
shovelhd's Avatar
 
Join Date: Jun 2010
Location: Western MA
Bikes: Yes
Posts: 15,383
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
41
shovelhd is offline   Reply With Quote
Old 04-13-14, 07:30 AM   #6
globecanvas
Ninny
 
globecanvas's Avatar
 
Join Date: Jan 2010
Location: The Gunks
Bikes:
Posts: 4,257
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Quote:
Originally Posted by tetonrider View Post
if your clearance is that tight, i'd give a minute to think about any debris getting caught and potentially damaging the frame and/or locking the wheel.
This does happen. I run 25s on my rain bike because they are comfy, but clearance under the brake bridge is minimal. A few weeks ago I got a piece of gravel stuck between the rear brake bridge and the tire, which brought me to a skidding halt. Luckily I was climbing a hill and not descending, and no damage was done, although the last thing I wanted to do at that moment was stop and get off the bike.
globecanvas is offline   Reply With Quote
Old 04-13-14, 07:56 AM   #7
gruntle
Junior Member
Thread Starter
 
Join Date: Mar 2012
Location: Seattle
Bikes:
Posts: 23
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by globecanvas View Post
This does happen. I run 25s on my rain bike because they are comfy, but clearance under the brake bridge is minimal. A few weeks ago I got a piece of gravel stuck between the rear brake bridge and the tire, which brought me to a skidding halt. Luckily I was climbing a hill and not descending, and no damage was done, although the last thing I wanted to do at that moment was stop and get off the bike.
Seems like 25s might not work out on this frame. I have ridden a several days on wet mucky roads when my winter bike was not available. The road debris was enough to rub off the paint.
Yesterday I rode a new route on a paved trail that turned to gravel, while nothing got full on stuck with my 23s the tire brought enough gravel pieces through to wear down to carbon fiber!

I may go with wider rims for other benefits but it seems 25s are not going to happen on this bike.
gruntle is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 02:23 AM.