REAR TIRE CUPPING - CAUSE???

[timonbik]

This is not pertaining to my 750 Breva but I value the opinions and the experience of fellow forum members.
I have a Honda NT700 V also known as the Deauville in Europe.  When I bought it with 10,000 miles on the odometer it had Bridgestone BT20's on it with plenty of tread left but severely cupped.  I managed to put on 3000 noisy miles before changing them. Still had another 1000 miles in them but was heading on a trip and didn't want to have tire problems so I put on a set of Nankings.  I've put a little over 3000 miles on the new tires which are already starting to show signs of cupping on the rear.  Front is good.  I'm a fairly heavy guy at 225lbs and we do ride 2 up a fair amount.  Bike is equipped with a top box.  It has been extremely hot here with temps approaching 100.  Rear wheel bearings were changed when the tire were replaced.  Bike handles superbly.  I've had many bikes and gone through many tires but never experienced such pronounced cupping. 
Any suggestions/comments would be appreciated.
Thanks, Tim

[normzone]

I'm not an expert, and I don't even play one on television, but I thought cupping had to do with suspension.

[fotoguzzi]

what tire pressure are you running.. If I was carrying that load I'd be up around 42psi.

[timonbik]

Around 40 psi.  Going to bump it up to 44 to see if it makes a difference.
Tim

[Chuck in Indiana]

I've never had rear tire cupping, so I'm no help. Fronts? Yeah. I'll be interested to see what you come up with.

[fotoguzzi]

I had that happen on two rears (in the 90's), Michelin Macadams I think they were.. have not bought a Michelin since..
so, could be tire choice, switch to something else and see?

Maybe try complaining to the manufacturer?

[charlie b]

The best tire I had on my NT700 was the PR3's.  Mine had about 8k miles on them and were just starting to show some wear when I sold it.  The PR4's have had a spotty response, as in some got horrible mileage while others got a lot.  Avon Storms worked well but the rear only lasted 8k miles.  Stock tires were about same mileage but worse handling.

I only rode solo so never experienced cupping on the rear.  If I loaded up the bike I'd bump the pressure to compensate, also add preload.  I was also a bit over 220lb when I had mine.

Short answer, I'd replace the tires with some better ones and keep the pressures up when riding with a passenger.

[Arizona Wayne]

I say the rear shock(or is it shocks) are shot(too soft?)   I'll bet the rear suspension is bouncing up & down most the time.    If that's the case, air suspension should fix the issue. 

[Perazzimx14]

If I got 13,000 miles out of a rear tire I'd do a happy dance.

[Two Checks]

Sometimes it is just the design of the tread pattern causing the cupping.

[charlie b]

If I got 13,000 miles out of a rear tire I'd do a happy dance.

The PR3's on the NT700's would go between 15 and 20k miles of highway riding (not track and not two up).  One guy had 25k on one before he changed it.  I tended to get much less mileage than some of the rest.

On the T5 I can't get a tire to go more than 10k and most of the time I am lucky to get 8k.  The Sport Demon I had only got 6k.  I wish they made PR3's or similar for my 16" wheels.

[charlie b]

I say the rear shock(or is it shocks) are shot(too soft?)   I'll bet the rear suspension is bouncing up & down most the time.    If that's the case, air suspension should fix the issue. 

That could be the case.  I know the rear shock was good for me (225lb) and 100lb of camping gear.  Not sure if it would handle much more.  Some of the guys did fit aftermarket shock (one shock).  I probably would have if I had kept mine.

[redrider]

I have experienced this on all of my bikes to some degree. The V11 w/ Michelin PR's and Dunlop Roadsmart were especially bad. Front and rear, BTW. No evidence of cupping w/ Avon Storm 3D XM until the last 100 miles or so on the rear only. (The wear bars were just barely starting to blend with the outer surface). I will offer that tread design and carcass construction are the major factors that conspire with de-acceleration loads to produce cupping. Every time you use engine braking, the rear tire is being loaded with forces opposite of what the tread design is optimized for. High capacity twins generally have great engine "reverse torque". Most cupping on the front is also due to the weight transfer when slowing, either with engine or mechanical braking. Tire pressure affects wear mileage more than anything unless the pressure is routinely run very low. Gold Wings are especially susceptible to front cupping. Many tire brands and designs have been tried with varying amounts of relief. Resist the temptation of over inflation. There be monsters.

[CalvinHobbes]

Incorrect rebound dampening. Tire is not staying on the road-bouncing up and down uncontrollably. This causes the tire to skip and rub away rubber as it recontacts the ground causing the cupping of the tires.

[Two Checks]

If the cupping is at the leading edge of the grooves it is due to the tread design.
The leading edge of thegroove contacts the pavement and flexes cauing more wear at the contact point.
This is not my opinion, it is from the guys at Continental tires.

[John Ulrich]

Put bike on center stand. Start it, put it in a higher gear and use a Surefoam rasp plane to knock down the high spots.  Of course this is only professionals under controlled conditions, results may vary.   

[atavar]

How about a good burnout on a grated bridge?

NO!! DON'T DO IT!  I'M KIDDING!

[PeteS]

Sometimes it is just the design of the tread pattern causing the cupping.

Agreed. Its pretty normal especially if you have a heavy wrist. Same reason front tires cup if you brake hard a lot. More noticeable on big block tires like dual sport rather than sport bike tires with just grooves.

Pete

[Penderic]

By design ....



You can ride up the sides of skyscrapers with these babies!

[timonbik]

Thanks for all the input.  I truly appreciate it.  I think it is a combination of factors affecting my tire: tread design, 2 up riding, extreme heat an s little aggressive riding.  I do like to lean into the corners.  I think all of this might have been exasperated by the tire air pressure being marginally low.  Will pump them up a bit to see if I can slow the process down.
Thanks, Tim

[Chuck in Indiana]

Agreed. Its pretty normal especially if you have a heavy wrist. Same reason front tires cup if you brake hard a lot. More noticeable on big block tires like dual sport rather than sport bike tires with just grooves.

Pete

The fronts used to cup pretty badly on the Centauro, only on Bridgestones, and at the leading edge of the grooves. I quit using them, even though they were.. uh.. inexpensive. (Guzzi content)

[redrider]

Low air pressure causes low mileage. I run 42, the max recommended by Avon, in the rear and 36-37 in the front. I do notice a bit of wear difference on the rear. The outside portion near the sidewall looks a bit more wrinkled. I do love to goose it once past the apex. What's for dinner? It ain't chicken strips.

[Perazzimx14]

The PR3's on the NT700's would go between 15 and 20k miles of highway riding (not track and not two up).  One guy had 25k on one before he changed it.  I tended to get much less mileage than some of the rest.

On the T5 I can't get a tire to go more than 10k and most of the time I am lucky to get 8k.  The Sport Demon I had only got 6k.  I wish they made PR3's or similar for my 16" wheels.

If I got 15 or 20K out of a rear tire I'd do backflips.

[Chuck in Indiana]

If I got 15 or 20K out of a rear tire I'd do backflips.

I've never gotten over 6. 15 or 20???

[Arizona Wayne]

On all my bike tires, no matter the load, I run max tire pressure on the back and near the same on the front.  Only time I get cupping on the front(no matter the tire) is when I forget to monitor its tire pressure.   I always try to get max mileage possible out of my tires, even when the tread is flat from not enough curves to wear the side treads.  Then I adapt to the feel of my tire, not replace the tire until it's truly worn out.   

[Perazzimx14]

I've never gotten over 6. 15 or 20???

That more like what I get out of twin cylinder bikes. The DR with street only tires and an FCR carb gets about 2.8 to 3K before the rear tire is shot.