BMW R1200RT/R1250RT Forum

Hi all!  I just changed out my front and rear tires, and noticed slight cupping of the front tire, but the rear wore very well.  I'm always on top of tire pressures, and have been 36 front / 42 rear all the time, varying by 1 or 2 PSI max.  The tires were Pilot Road 4's (not GTs, but the new set are).  Can anyone tell me why the front would cup slightly?  Does this indicate tire pressures are low, high, or something else entirely?  I was able to get about 12,000 kms out of the pair, so I'm happy!


Nothing beats new skins on a bike at the start of the season.

That's a good mileage for the wrong type of tyre for the bike so you did well. Mind you you are the second owner who has recently had an issue with front PR 4s.  And I've just ordered a set after years on Z8s. Should I change my order maybe?

No don't change your order try them. I think they are a very good tyre IMHO better than Z8s. I've got Angel GTs on my RT but will be changing them to PR4GTs. Have PR4GTs on my Pan ST1300 and they have performed very well. Just about to replace with same. Mileage nearly 8000. For a heavy bike thats amazing. Will be interesting to see how they perform on the RT.

Just been reading a thread over on another forum and the topic was a discussion on an above average incidence of punctures with PR4s. People were offering lack of steel belting and the apparent lack of substance in the carcass (indicated by their high flexibility) as possible causes. This led one or two people to think about a different make next time. Of the three punctures that I am aware of having in the last 19 years, 2 have been on PR4s within a month of each other and all three when I didn't have Ultraseal/Puncturesafe in the tyre. Agree that they perform well but have gone for Avon Storm 2 Ultra this time.

That's done it.  Back to Z8 for me.

RTman10 wrote: That's done it.  Back to Z8 for me.

I'm giving the PR4 GTs a second chance - mainly because the non-GT version were so good on previous bikes.


I'm willing to accept that the front one on the RT was a Friday afternoon tyre.  I f it happens again, Z8s it will be...

Well the last puncture I got on my RT was with Z8s so obviously they are no good ! No seriously I really cannot see how one tyre is better than another at avoiding punctures. As I ride all year my main consideration is wet weather grip and the PR4GTs have not yet let me down.  Personally I have found that they have more feel and turn in faster than Z8s. Having said all of this tyres are very much a personal thing, fit what your happy with and ride.

Agree that the PR4 is a good tyre, wet grip etc, etc. Just don't recall another thread where a specific tyre has been discussed in the same fashion. Three pages and quite a number of posts relating to multiple punctures. I don't presume to know enough about the various makes of tyre and their construction to come to a judgement regarding their puncture avoiding capabilities. Just passing on what some others think and my own personal experience. Food for thought though.

http://www.ukgser.com/forums/showthread.php/418743-Pilot-Road-4-amp-Punctures?highlight=punctures

Interesting findings.  But back to my original point - what causes cupping?  Is it too low pressure?  Too high?  Am I being a hooligan?  I was very happy with the distance I got out of them, and SUPER happy with the way they handle in the warm, in the cold, in wet and dry conditions.  All around, I can't imagine things getting much better than the Michelin Pilot Road 4.  Too clarify, the new front is a Pilot Road 4 and the rear is a Pilot Road 4 GT.  About 2 years ago when the Pilot Road 4 first became available, there was no GT model front - they put the PR4 front and on some bikes (larger, more powerful bikes) they put the PR4 GT. 


So what causes cupping?

This came from the Dunlop website.


You may not be able to entirely avoid cupping. Tire cupping or irregular wear is a somewhat common occurrence on all vehicles. On a four-wheel vehicle, you are advised to rotate your tires periodically to even out wear. Unfortunately, you do not have this luxury with a motorcycle because front and rear tires, unlike those on most four-wheel vehicles, are not interchangeable.[/font][/size]
However, there are steps that can be taken to minimize cupping and uneven wear on a motorcycle: Maintain your motorcycle and particularly your front and suspension. Avoid hard braking whenever possible. Braking causes the tire to grab and wear in one direction. When braking is applied to the front tire, the load transfer over-flexes the tire and increases the tendency for cupping and uneven wear. Maintain your tire pressures. Under inflation and overloading of motorcycle tires are significant causes of cupping and uneven wear, particularly in association with hard braking and/or trailer use.[/font][/size]
Once a tire begins to show signs of uneven wear, even following these steps may not improve the condition.[/font][/size]
Tire companies can, and are, helping to minimize cupping and uneven wear but you, the rider, must do your part. Following the aforementioned guidelines will help avoid uneven wear.[/font][/size]

I followed some sage advice from my mom...  "duuuh, google it"...


My findings:
http://www.rattlebars.com/tirewear/index.html :
[size=medium]The first question to be addressed is "What is tire wear?"[/size][size=medium] Tire wear is the actual [/size][size=medium]removal[/size][size=medium] of rubber from your tire. [/size][size=medium]Scuffing[/size][size=medium] is what wears out your tires. Just like when you were a kid and skidded your rear bicycle tire to make marks on the driveway, the abrasion of scuffing is the [/size][size=medium]only[/size][size=medium] contributor to tire wear. If you never scrubbed anything off your tires, they would never wear out. It takes some pretty good stiff forces to come into play for pavement to scuff stuff off of your tires. This scrubbing of material off your tires becomes evident in what is called [/size][size=medium]cupping[/size][size=medium], [/size][size=medium]flat band upright tire wear[/size][size=medium] which presents itself most evident on the rear tire and [/size][size=medium]side flat band tire wear[/size][size=medium] which presents itself most evident on the front tire. All of these wear patterns will be discussed and all are present to some degree on both the front and rear tire. But in the following discussion, it is important to remember that it takes a goodly amount of force where your tire meets the road to grind material off of your tires to produce tire wear. Too, we assume that you will run with properly inflated tires. Improperly inflated tires will cause all of these wear patterns to be greatly exaggerated and will cause you to lose many many serviceable miles. Check pressure often. Empirical evidence for Valkyrie, GL1800 and VTX tires shows that running 38/40, 40/40 or 40/42 (or slightly above/below) will greatly extend tire life. The Honda spec of 33psi for these bikes is way too low and is designed for maximum comfort and grip but minimum tire life. Increasing the pressures to some combination of the above will provide increased longevity and improved handling for these tires.[/size]
[size=medium]
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[size=medium]Interesting!!![/size]
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This may explain why I don't suffer from front tyre cupping. I'm generally a very light user on the brakes. My riding style is smooth. I like to accelerate and ride at a good pace but hate hard braking. So I guess I'm easy on tyres. Tyre pressures are always spot on. Part of my pre-flight check. Old habits ....It also mentions suspension. I guess if its worn or not setup correctly it could effect front tyre wear. How that would relate to a RT I don't know.

My non dealer bike shop says use 40/40 on PR4GT and you avoid some cupping, but they will still cup a little, don't worry about it with that kind of mileage!

My non dealer bike shop says use 40/40 on PR4GT and you avoid some cupping, but they will still cup a little, don't worry about it with that kind of mileage!


Don't take his advice.  Tyres are a critical safety item and should be run at the right pressure. 

RTman10 wrote: My non dealer bike shop says use 40/40 on PR4GT and you avoid some cupping, but they will still cup a little, don't worry about it with that kind of mileage!


Don't take his advice.  Tyres are a critical safety item and should be run at the right pressure.

I'm with RTman on this one - although I have to admit to the odd experiment with different pressures to see what happens to the handling...