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Should a 120 lb. Rider run narrower tires ?

1K views 10 replies 10 participants last post by  Varaxis 
#1 ·
I bought my daughter a XS 2011 BMC Trailfox it's due for some new tires she's about 120lbs. Riding what would be considered xc to trail , but we are going to Colorado soon. I'm thinking 2.3 front 2.1 rear. Is there a point where you are not getting enough weight on threads for good grip? Lighter rider = less tire pressure ? Throw in some good front rear combos if you want.
Google is less helpful as it once was finding questions , instructions , manuals ect. puts way more store hit's first.
 
#2 ·
While I feel that heavier riders benefit from larger tires (so they can run lower pressures without pinch flatting or damaging rims), there's no need to specificaly run narrower tyres for lighter people. Just adjust air pressure. At that weight she may be able to get away with lighter casings too, which is always nice.
 
#3 ·
A lighter rider generally requires less pressure. Narrow tires are fine, but anyone can find some benefit from larger tires too. Larger volume tires roll over obstacles better and don't get stuck between roots and rocks as easily so handling in technical terrain is easier. That is part of the reason the fat tire bikes are so popular, they roll over obstacles easier.

Handling and traction are greatly affected by weight transfer and the skill of the rider. Fresh knobby tires will generally make cornering easier for anyone though.
 
#4 ·
I think slightly narrower tires for light riders may be a good option for some situations because of the weight savings, proportionally weight affects lighter riders more than it does heavier ones. I think wider tires will generally grip better regardless of rider weight though.
 
#5 ·
I think wider tires will generally grip better regardless of rider weight though.
Consider this: Two riders, one at 250 lbs, one at 125 lbs, both running the same 2.3" tire on the rear. The weight distribution is the same (40/60 front/rear), so the load is still double that on the rear tire of the heavier rider compared to the lighter rider. The lighter rider is running half the inflation pressure of the heavier rider, so the area of the contact patch is equal. That results in half the pressure distributed through the contact patch for the lighter rider.

There are two forms of friction between a mountain tire and a typical trail. On a wet or slippery hard surface, and large contact patch and lower pressure distribution is best. But on a loamy or loose trail surface, a higher pressure distribution results in better knob penetration and greater mechanical traction from the tire's tread.
 
#8 ·
In short, no. Thinner casings that provide better compliance and lower pressure, yes. At 120 pounds, she can run about 20-22 pounds and get great traction and handling.


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#9 ·
A lot of factors come into it - in terrain with sharp rocks etc a light carcass is as easily sliced under a light rider as a heavy one in my experience.

Further, while it's tempting to say that a light rider can run really low pressures in a light tyre, there comes a point where the tyre will fold and wallow and feel vague.

It's really a try it and see thing IMO, though there are some obvious things like the sharp rocks I mentioned earlier.

TBH, I think it you avoid extremes either way you'll be fine - a knobbier 2.25 or similar up front with a good "true sized" 2.0 or 2.1 on the back with a tread pattern to suit the terrain (loose, scrabbly or hard packed) would be a good bet IMO.
 
#10 ·
I have mixed feelings.

When I moved to Seattle, I weighed 136 lb and felt pretty well served by 2.1" tires. During grad school, I gained 40 lb and started flatting, so I had to increase pressure, which made the ride harsh. The whole Internet said wide tires are better, so I gave a set of 2.25s a shot. I got back down to pressures I like, and was happy. I mean, I was still stressed out, I was in a situation that contributed to packing on 40 lb. But my tires were working nicely for me.

A few years later, I have a job, I've dropped the 30 lb I want to (136 was always too low) and I'm still feeling pretty good about wider tires. I have nominal 2.4s, that measure about 2.3, right now.

I think there's an effect of spring force vs damping going on. I think someone who feels like she goes straight from sluggish to harsh, or needs to run squirrelly-low pressures to get a smooth feeling from a tire, might be better served by narrower.

If 120 lb is light enough to be badly served by 2.3s, I dunno.

Are we talking teenaged daughter with opinions of her own and some curiosity about her gear? Smaller child? Petite adult? Since this is all about the experience of another person, it would be a great thing for her to take ownership of herself if she's ready and interested.
 
#11 ·
I'm 135-140 lbs. I highly recommend the Ikon 2.2 EXO TR 3c. They're my favorite tire for 3 years now, made even better when they made a TR version. Every non-DH tire I have are merely beater tires that I am trying to wear down on pavement now. I have about 8 of them equipped on various bikes in my quiver. I feel no sting when I pay the $65 or so per tire. I believe tires are one of the best places to spend for pure performance, if not *the* best.

I've run narrower Vee Rubber 2.1 (were more like 1.9 visually) tires to avoid wearing down my nice tires on pavement, and found that they ride surprisingly well. I didn't want to experiment with tubeless, seeing its plain bead, but its tough casing warded off flats well enough running tubes. I didn't really suffer at slip until it started getting balder, but still ran it to squeeze more mileage, since it was fun getting sketched out and confronting the challenge of having less grip made things interesting. I credit the rubber compound, which seemed like a Maxxis MaxxPro 60A, but it wore out in 25% of the typical mileage I get out of an Ikon.

I've run wider Racing Ralphs. They squirm a lot, folding when I push them. I don't have much confidence in them. In the rear, they like to fall into ruts, needing a lot of encouragement to roll out of them, and likes to drift out on off camber turns. I suspect that the way the shoulder knobs are oriented and staggered makes it "walk" in an inward direction (left shoulder knobs want to go right when engaged). When I get going pretty fast and start to flow, they are buzzkills, tending to burp and feel like they're going flat. If I don't pump the bumps, or at least don't unweight the wheel, their bounce is a bit violent. It feels like an air spring with virtually no damping, the way its ballooned out nature bounces.

I've looked at the 2.35 version of the Ikons, and see they're scaled up. Seemed similar to how the Ardent 2.4 is so different than the 2.2 version, so much that it's almost a different tire. I actually bought one, but haven't found a bike I wanted to equip it on yet. That's the main reason I don't go bigger, since there's nothing with the tread pattern and profile and other features I want. The next step up is the plus sized range of tires, 2.7-3.0. Doesn't help that I only have 19-21mm ID rims right now that I like, with the exception of an I9 Enduro with Stan's Flow rims, which I've had on backup but probably should sell.

I've tried Nobby Nics, the new 2015 ones, on 941 Ibis rims, and bottomed it out on a tiny 1.5' drop to slight uphill (same drop makes a 2.35 tire squirm/twist on normal width rim, but not bottom out). I was not very convinced by the high volume trend in general, besides how the traction was more than adequate and how it didn't have low pressure squirm when pushed in the corners when combined with wide rims. I have my doubts if it's a decent substitute for just having a stout casing. Would need a longer term test to confirm. Riding a friend's heavier built Enduro 29, letting him ride my lighter built E29, I thought the DHF on Roval Fattie SLs cornered extremely easily. Felt like I could push it so much harder and tighter around bends than I usually do.
 
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