A Tire Pressure Question

[IRBR]

My 2005 FJR Owner's Manual states in the Specifications section:

Loading condition: (0-198 lbs.) Rear - 36 psi

Loading condition (198-443 lbs.) Rear - 42 psi

High speed riding Rear - 36 psi

__________________________

This information contradicts most of my knowledge and experience regarding heat, loading, and tire pressures.

If a car or truck tire is subjected to a heavier load, it is required to be inflated closer to its maximum pressure.

I can only deduce that the increased speed produces more heat, higher tire pressures, and therefore the recommendations for a lower pressure under load at speed is to prevent higher than safe tire pressures.

__________________________

What prompts this post is that I am having to replace my Metzler Roadtec Z6 tires before they are worn to the wear indicators, at only ~4000 miles of riding. For the first time in 9 motorcycles and ~80,000+ miles of riding, I have cupping on my rear tire. In fact, it is the most severe cupping I have ever seen.

I am wondering if my wife and I riding at highway speeds (75-90 mph) with a rear tire pressure of 36 psi could in any way account for this phenomenon.

If anyone has any insights into these several, possibly interelated subjects, I would appreciate your responses. I have just purchased a set of Michelin Pilot Road tires to replace the Metzlers and I don't won't a repeat of this problem.

IRBR

 

[FJReady]

Owner's manual?? This is the FJRforum. You don't need no steenking owners manual any more.

No seriously, I think you find that most riders around here keep the rear above 40 psi (cold) all the time. When the FJRs started showing up with Bridgestones in 05 much to the delight of those who had trouble with the Metzlers of prior years, there was some (OK, alot of) discussion about cupping causes. IIRC the cupping was mosly attributed to under inflation.

I've never had any heat/grip/cupping issues with either Avons or Bridgestones. I typically run 40 front, 42 rear. 95% of my riding is solo. If I'm on a long trip with passenger and/or additional gear, I'll bump up the rear to 44.

My $.02

Russ

 

[SkooterG]

Tire pressures is as much art as it is science. Many of us use higher pressures. Just take a look around the forum it's been covered a zillion times.

The official line I have read is that one of the major contributors to cupping is too low or too high of tire pressures. Well, I personally haven't noticed higher pressures leading to cupping, but have noticed lower pressures causing it. I think 36 psi is way to low for higher speeds, and expecially two up.

I would up your rear tire pressure to 42+ psi, and perhaps try a different brand of tire.

 

[cougar8000]

You ride two up and still keep it at 36? That would be your explanation IMO. Pump it up to at least 41 unless you and the misses are not braking 198 load

 

[85turbo]

i know its not related (maybe it is?) but the owners manual for my o6 states

39psi cold front, and 42 psi cold rear.

these pressures seem to be higher then the gen 1 manual.

maybe yamaha noticed a lot of premature wear, and bumped up the recommended

pressures on 06+ bikes ?

i am at almost 7k km on the factory fitted Metzler Roadtec Z6's and both front and rear

are still looking good.

jason

 

[teerex51]

IRBR

I checked the Gen. 1 Workshop Manual and it recommends 290 Kp or 42 psi for the rear tire.

I don't have an Owners Manual in English so I cannot tell you whether it really says 36 psi for high-speed riding. If it does, it contradicts my own experience and convictions, too.

Stef

PS: Your avatar looks familiar. Are we related?

 

[IRBR]

Thanks, guys. I think some additional air in the rear tire is the answer. I'll do it.

And, yes, TeeRex51, we might be related. I, too, noticed the resemblance.