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


Go Back   > >

Mountain Biking Mountain biking is one of the fastest growing sports in the world. Check out this forum to discuss the latest tips, tricks, gear and equipment in the world of mountain biking.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-06-06, 11:59 PM   #1
bfloyd
Senior Member
Thread Starter
 
Join Date: Apr 2006
Location: Ohio
Bikes: vintage Raleigh
Posts: 654
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
different tire widths for front and back

I have seen people who use a different tire width for the front than the back. Example, I know some who use a 2.0 on the front and a 1.5 on the back. I understand that the wider tire in the front will aid in overall control but what is the advantage of the narrower tire in the back? Perhaps a lower rolling resistance seeing how the steering control isn't needed in the rear??? Thanks.
bfloyd is offline   Reply With Quote
Old 07-07-06, 01:42 AM   #2
blue_neon
Elite Rep
 
Join Date: Aug 2004
Location: Melbourne - Australia
Bikes:
Posts: 2,096
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Rolling resistance could one...
blue_neon is offline   Reply With Quote
Old 07-07-06, 06:33 AM   #3
mihlbach
Senior Member
 
mihlbach's Avatar
 
Join Date: Dec 2005
Location: Long Island, NY
Bikes:
Posts: 6,400
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Ask this in the BMX forum...thats where this practice originated. My understanding is that using a narower rear tire allows you to run higher pressure, giving you less rolling resistance. And the bigger front gives you better traction in the turns.
mihlbach is offline   Reply With Quote
Old 07-07-06, 09:23 AM   #4
Maelstrom 
Wood Licker
 
Maelstrom's Avatar
 
Join Date: Apr 2002
Location: Whistler,BC
Bikes: Transition Dirtbag, Kona Roast 2002 and specialized BMX
Posts: 16,885
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
wasn't this asked yesterday? You might want to look at yesterdays posts, the answer is in there.
Maelstrom is offline   Reply With Quote
Old 07-07-06, 09:29 AM   #5
nickw
Senior Member
 
Join Date: Dec 2005
Location: Portland, OR
Bikes:
Posts: 461
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Quote:
Originally Posted by Maelstrom
wasn't this asked yesterday? You might want to look at yesterdays posts, the answer is in there.
I believe it has to do with the fact that the rear is just accelerating you, who cares about tire width on the back. You can save the weight by running a smaller tire with no drawbacks. I personally like the way a small tire feels on the rear, feels more 'precise' but I ride the mtb like its a 20" so it might just be me-
nickw is offline   Reply With Quote
Old 07-07-06, 10:41 AM   #6
willtsmith_nwi
Senior Member
 
Join Date: May 2004
Bikes:
Posts: 1,398
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Bahhhh ... and 69/96

Quote:
Originally Posted by mihlbach
Ask this in the BMX forum...thats where this practice originated. My understanding is that using a narower rear tire allows you to run higher pressure, giving you less rolling resistance. And the bigger front gives you better traction in the turns.
A lower pressure on a larger tire will give you the same rigidity.

To answer the original posters question, mudders are fond of smaller rears because they "dig down" better. Larger tires float and mudders don't like that. There is likely a perceived rolling resistance advantage to a smaller tire. On paved surfaces this belief is justified, on irregular surfaces it probably is not as the ability of the tire to conform to the terrain allows the bike to travel straight rather than bouncing. Every bump translates into lost momentum (this is the advantage of larger tires).

Another reason that some prefer a smaller tire in the rear is the perceived "responsiveness" of the bike. Advocates of smaller tires will point out (deceptively correctly) that a larger tire means greater rotating weight and this translates into a larger moment of inertia. They perceive that this will slow down their acceleration. They also perceive it as they ride (quite correctly) as the larger diameter wheel package effectively changes the gearing. They fail to do the actual calculations to discover that the rotating 20 grams difference in the tire compared to mass of their body is practically insignificant. The effective gearing change re-inforces a physics fallacy and hence a smaller wheel in the rear.

Finally, the #1 reason to run a larger front than rear ... because you typically can. The chainstays of a frame are typically more confined than fork stanchions. A lot of people can only run a 2.1" on the rear even though they may prefer a 2.3" which will fit easily on the front.

This perception is so strong that it is leading manufacturers to produce "96er" bikes with a 29er in the front and a 26er in the rear. The theory is that the larger front wheel will reduce rolling resistance over obstacles while a smaller rear wheel provides quicker acceleration. The production of these bikes with medium travel front forks and hard tails is just laughable when you carefully consider it. You place suspension on a better rolling wheel and no suspension on poorer rolling wheel. It's a double shrug when you realize that you can just tweak the gearing of the bike (lose 2 teeth in front or add 2 in the back) to account for the "sluggishness" of the larger wheel). I suspect that the engineers run the numbers and shrug their shoulders as the market perceives this ... so it is so.
willtsmith_nwi is offline   Reply With Quote
Old 07-07-06, 10:44 AM   #7
willtsmith_nwi
Senior Member
 
Join Date: May 2004
Bikes:
Posts: 1,398
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Weight Weenies anonymous ...

Quote:
Originally Posted by nickw
I believe it has to do with the fact that the rear is just accelerating you, who cares about tire width on the back. You can save the weight by running a smaller tire with no drawbacks. I personally like the way a small tire feels on the rear, feels more 'precise' but I ride the mtb like its a 20" so it might just be me-
What gets me is that the people who should be most concerned about grams, endurance racers, are starting to turn to much bigger tires in the form of 29ers. This is the group for whom those extra grams REALLY add up to LOTS of spent energy through accelerations and climbing. The success of 29ers in endurance racing should really put this "big slow" wheel issue to rest.

A larger diameter wheel changes the effective gearing. This is where the perception comes from. You wouldn't be afraid to add larger rings to a 24" bike. Why be afraid of switching to smaller ones for a larger wheels?
willtsmith_nwi is offline   Reply With Quote
Old 07-07-06, 10:54 AM   #8
bfloyd
Senior Member
Thread Starter
 
Join Date: Apr 2006
Location: Ohio
Bikes: vintage Raleigh
Posts: 654
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by willtsmith_nwi
A lower pressure on a larger tire will give you the same rigidity.

To answer the original posters question, mudders are fond of smaller rears because they "dig down" better. Larger tires float and mudders don't like that. There is likely a perceived rolling resistance advantage to a smaller tire. On paved surfaces this belief is justified, on irregular surfaces it probably is not as the ability of the tire to conform to the terrain allows the bike to travel straight rather than bouncing. Every bump translates into lost momentum (this is the advantage of larger tires).

Another reason that some prefer a smaller tire in the rear is the perceived "responsiveness" of the bike. Advocates of smaller tires will point out (deceptively correctly) that a larger tire means greater rotating weight and this translates into a larger moment of inertia. They perceive that this will slow down their acceleration. They also perceive it as they ride (quite correctly) as the larger diameter wheel package effectively changes the gearing. They fail to do the actual calculations to discover that the rotating 20 grams difference in the tire compared to mass of their body is practically insignificant. The effective gearing change re-inforces a physics fallacy and hence a smaller wheel in the rear.

Finally, the #1 reason to run a larger front than rear ... because you typically can. The chainstays of a frame are typically more confined than fork stanchions. A lot of people can only run a 2.1" on the rear even though they may prefer a 2.3" which will fit easily on the front.

This perception is so strong that it is leading manufacturers to produce "96er" bikes with a 29er in the front and a 26er in the rear. The theory is that the larger front wheel will reduce rolling resistance over obstacles while a smaller rear wheel provides quicker acceleration. The production of these bikes with medium travel front forks and hard tails is just laughable when you carefully consider it. You place suspension on a better rolling wheel and no suspension on poorer rolling wheel. It's a double shrug when you realize that you can just tweak the gearing of the bike (lose 2 teeth in front or add 2 in the back) to account for the "sluggishness" of the larger wheel). I suspect that the engineers run the numbers and shrug their shoulders as the market perceives this ... so it is so.
Very interesting. Didn't time trialists at one time use different diameter wheels in the front and back at one point?
bfloyd is offline   Reply With Quote
Old 07-07-06, 12:24 PM   #9
superstator
Man about town
 
Join Date: Oct 2004
Location: Portland, OR
Bikes: '04 Giant OCR1, '85 Team Fuji
Posts: 105
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by bfloyd
Very interesting. Didn't time trialists at one time use different diameter wheels in the front and back at one point?
Yeah, but that was an aerodynamics issue. A smaller wheel generates less drag both due to spoke length and frontal area. Trackies used them for pursuits a lot. Different sized wheels are generally frowned upon by the judges these days, though.
superstator is offline   Reply With Quote
Old 07-07-06, 12:40 PM   #10
Grasschopper
He drop me
 
Grasschopper's Avatar
 
Join Date: Jul 2004
Location: Central PA
Bikes: '03 Marin Mill Valley, '06 Cannondale Rush, '02 Eddy Merckx Corsa 0.1, '07 Bottecchia Euro Sprint Tour Comp Elite Pro 1000
Posts: 11,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
When I raced I did it because it was just plain faster. Less rolling resistance for sure and I was running a 1.9 in the back. Also back then we didn't have suspension so the larger front gave a bit of shock absorbtion as well as added traction.
__________________
The views expressed by this poster do not reflect the views of BikeForums.net.
Grasschopper is offline   Reply With Quote
Old 07-13-06, 05:16 PM   #11
literocola
Your Local Megalomaniac
 
literocola's Avatar
 
Join Date: Mar 2006
Location: Centennial, CO
Bikes: Gary Fisher GED, ECHO Pure, Norco Moment, Kona Stab
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Matching 2.5's on the assult/ do it all beat machine

2.7" Maxxis Rear, 2.35" Try-All trials tire on the Trial Rigs.
literocola 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 11:49 PM.