TCR

Would a brand new set of tires be faster than the same exact pair that have 3000 miles on them and have flattened out? What do you say?

Enthalpic

I would say slower because of more material to move around; plus the material would probably be stiffer.

Don't worry I will let you upgrade to my worn tires if you send me some of your new ones. As an added bonus they weigh less!

DannoXYZ 

Yeah, I think tyres are best right before you throw them away. The wide flat contact area deforms less with less rolling-resistance than the convex shape of a new tyre. The lower weight also gives faster acceleration in sprints and faster hillclimbs.

flyingasics

Hmm I would dissagree I think. I usually ride mine to the threads and it always feels as if new tires are so much faster. I would think the weight difference between a new and old tire is negligable, and that less contact area with a new tire would be more of a factor.

Impoliticus

I can't imagine there's much of a difference, but I would expect SLIGHTLY more rolling resistance with an older tire because of a larger contact area and slightly less weight with an older tire. The two factors probably come very close to balancing themselves out.

noisebeam

If you use a cyclocomputer that counts rotations on the rear (the wearing) wheel, does the reduction in radius (under no load) affect the radius of a worn tire (under load) enough to cause the computer to register (very slightly) higher speeds?

As a rough estimate a 1mm radius reduction would result in about a 0.3% increased in measured speed. This of course assumes that a 1mm reduction in rubber translates to a 1mm reduction in loaded radius. This would be the difference between the 'computer' reading 20.0mph or 20.1mph (20.06 rounded up)

Al

bbattle

Put those new tires in the freezer for 4 years, then ride on them.

TCR

Hmm, just wondering since I'm doing a TT this Sunday.

Older Flattened Tire:
More rolling resistnce since more surface is touching?
Less rolling resistnace since it's probably harder rubber?
More chance of a flat since less tread?
Faster since it's lighter because of less tread?
Flatter surface better for straight line time trialing?

New Tire:
Less rolling resistance because of roundness and less surface is touching?
More rolling resistance since the rubber is probably softer?
Less chance of flat since more tread?
Slower since it's heavier with more tread?


Oh well, I don't think it's going to make a difference either way. I'll just go with the old tires that are already on there and pedal my butt off.

nitropowered

I'd say a tire that has been worn in a few hundred miles. You'd get your rubber broken in and get all the manufacturing junk worn off.

Thats why race car teams usually ride tires in practice so they can wear them in a little so they get traction right out of the tire change.

DannoXYZ 

Contact area is only determined by air-pressure, not tyre-width (that just determines the shape). If you use the same air-pressure with old vs. new tyre, they will have same contact area. The shape will change as it wear, but the surface-area will remain the same. It's the bouyancy equations..

If you look up the chart on rolling-resistance tests, you'll see that wider tyres of the exact same model & construction has less rolling-resistance at the same pressure than the narrower version (Avocet 20/30 models in 25/28c). The narrower tyre has to deform more longitudinally in order to have the same contact-patch surface-area. You can measure it yourself based upon the rim's distance to the ground. Pump up a 28c tyre to 100psi and measure the rim-distance to the ground before and after sitting on it. Then do the same for a 23c tyre at the same pressure, you'll find that the narrower 23c tire will deform more and have a higher deflection for the same contact-patch area.

merlinextraligh

must be a long day at the office

TCR

Does anyone else see boobs and nipples when they look at that chart?

merlinextraligh

I repeat again long day at the office. and I go for the wide.

Starclimber

Experience says: Older, worn tires have lower rolling resistance, but less rubber to resist punctures. Two old tires (yes, yes, I know, it's madness to put worn front tires on the rear, according to legend) are noticeably faster than two new tires, assuming same model of tire. Maybe the OP can run a pair of short time trials employing old and new tires, and report back to us.

Johnny Rad

This was just the thread I was looking for today... I'm not going to replace my higher mileage tires (not threadbare) ahead of this week's hillclimb.

With my secret weapon aka well broken-in / worn-in tires, I feel confident starting to celebrate my triumphant ascent ahead of time.

Disclaimer: Unless I've missed another important thread...

jaxgtr

I've seen some old threads brought back to life, but 16 years has to be the all time thread from the dead revival

ThermionicScott 

Johnny Rad was a member when this thread was last current, so I'll give him a pass.

tempocyclist

His tyres must be well and truly worn in and ULTRA FAST by now!



In the 16 years since this thread was posted I'd say you've probably missed, ummm, zero important threads...

😂

Johnny Rad

Since I wasn't responding to the OP, I figured it wasn't a blatant procedural thread error.

I think what I did is called necro something or other.

LOL

ThermionicScott 

Some folks get way too bent out of shape about these things. Let us know how the hillclimb event goes.

jaxgtr

no issues from me, just thought it was funny. Good luck on your event.

Johnny Rad

It's all good and fun.

Besides, it looks like a verbal warning and not a written warning.

Hang-on, I see another old thread that needs necro whatever reviving...

Lucillle

New sneakers are faster than old ones.