Get The Sandwiches Ready - GSA Rear Wheel Collapse

[Deleted account 191119001]

I disagree, Knutk. The front wheel only has forward braking forces to deal with (Ok and turning and centrifugal but they aren't extreme enough, I don't think, and part of the design anyway). Under acceleration the rear wheel carries most of the weight and can increase it by quite some margin) as it does when you use engine braking and normal braking. Under normal braking the rear wheel wants to sink but is mitigated by the ESA and also carries a fair bit of weight.

The front wheel only really experiences extreme forces under hard braking. It also experiences stresses offroad but, again, designed for that with the caveat that the spokes should be checked. Offroaders (scramblers, enduro, pure ones, not big KTMs and the like) do not tend to be fast or used on motorways, much less with any luggage or pillion loads and they also tend to be much, much lighter.

I agree, the forces on a gravel or offroad surface are not the same as on tarmac where the traction is far greater.

Warlord, I don't think it would take much more than a couple of loose spokes at most to get the effect you are after in your experiment.

Hence some of the OP,s on here are getting wheels changed by BMW because of loose spokes, seems strange BMW would change a wheel because of loose spokes, must be more to that, they know something is wrong.

 

[Andy B]

Read what you will into this but my bike came back from its 12k service at Cotswold this week with paint on the front and rear calliper bolts.

Someone’s alive to the current debate ....

 

[Deleted account 191119001]

Read what you will into this but my bike came back from its 12k service at Cotswold this week with paint on the front and rear calliper bolts.

Someone’s alive to the current debate ....

Well makes sense, surely some BMW workers are in this forum, and probably spreading the word, next recall spokes changed for alloys...............

 

[topcat2006]

Read what you will into this but my bike came back from its 12k service at Cotswold this week with paint on the front and rear calliper bolts.

Someone’s alive to the current debate ....

Cotswold have done that the last few years when I got my bikes serviced by them.

 

[GrinningGSer]

Hence some of the OP,s on here are getting wheels changed by BMW because of loose spokes, seems strange BMW would change a wheel because of loose spokes, must be more to that, they know something is wrong.

Changed to alloys or changed for properly tensioned new spoked wheels ?
If there are lots of spokes out of tension then it is almost impossible to retention them, certainly as a diy job, because a special jig is required and BMW will not have that skill in house . I’ve read that wheel builders also have difficulty with these cross spoke BMW wheels . That said , it’s a simple job to retension one or maybe two spokes without affecting wheel trueness and the use of sound is your aid ; just like a guitar string .
( and warning you must back off or even remove the very hidden grub screw before turning the adjuster head )
Please report on this or another thread if you have lots of spokes loose ........

 

[knutk]

I disagree, Knutk. The front wheel only has forward braking forces to deal with (Ok and turning and centrifugal but they aren't extreme enough, I don't think, and part of the design anyway). Under acceleration the rear wheel carries most of the weight and can increase it by quite some margin) as it does when you use engine braking and normal braking. Under normal braking the rear wheel wants to sink but is mitigated by the ESA and also carries a fair bit of weight.

The front wheel only really experiences extreme forces under hard braking. It also experiences stresses offroad but, again, designed for that with the caveat that the spokes should be checked. Offroaders (scramblers, enduro, pure ones, not big KTMs and the like) do not tend to be fast or used on motorways, much less with any luggage or pillion loads and they also tend to be much, much lighter.

I agree, the forces on a gravel or offroad surface are not the same as on tarmac where the traction is far greater.

Warlord, I don't think it would take much more than a couple of loose spokes at most to get the effect you are after in your experiment.

If the combination of power and load of the bike is more than the wheel can handle, then what about Multistrada and KTM. They both have more torque and are more powerful. Do these bikes have problems with their spoked wheels?

 

[Deleted account 220214001]

If the combination of power and load of the bike is more than the wheel can handle, then what about Multistrada and KTM. They both have more torque and are more powerful. Do these bikes have problems with their spoked wheels?

Multistradas don't have spoked wheels. You may be able to fit them but I don't recall ever having seen a MS (standard out of the shop) with spoked wheels.

Have a look at KTM's spoke setup. As far as I can see they are traditional in that the spokes radiate out to the center of the rim, a strengthened center rim. The BMW ones don't, they go from the hub to the outside of the rim and they look thinner although there may be more of them. The spokes on the KTMs have much more clearance from the caliper than the BMW ones do.

 

[JohnnyBoxer]

BMW have been using these type of tubeless spoked wheels since about 1990, I'm sure they know the stresses and tolerances of them by now

Rims are Behr and they might make them for BMW, however they might not be Behr on the latest WC's, have a lot at your rims

BMW spoked tubeless wheels are reknowned for being v strong

I have seen forks completely twisted and shattered after a crash, however the Behr rimmed wheel is completely intact and not bent

 

[GrinningGSer]

Multistradas don't have spoked wheels.

Yes they do if you purchase the enduro model , with its 160bhp.
I am sure, as all of the above posts have suggested , that bhp is NOT the issue , because this is a well established and well proven product and many really rag their engines .

 

[fred_jb]

Yes they do if you purchase the enduro model , with its 160bhp.
I am sure, as all of the above posts have suggested , that bhp is NOT the issue , because this is a well established and well proven product and many really rag their engines .

Not an issue if nothing has changed with the manufacture or spec of the wheels and spokes, but as seems to have happened with BMW and others, problems can occur with a change of supplier and/or when cost reduction exercises take place which change the design - have we already forgotten the change in fork crimps saga?

 

[GrinningGSer]

FWIW, the 160bhp multistrada enduro has similar , spokes to the outside rim , configuration as our GS’s

 

[Deleted account 220214001]

Yes they do if you purchase the enduro model , with its 160bhp.
I am sure, as all of the above posts have suggested , that bhp is NOT the issue , because this is a well established and well proven product and many really rag their engines .

Absolutely correct, of course, my bad. Not sure what the sales figures are for them but they have chosen not to add it to the 1262 update to date (or have I got that wrong as well? I don't much go for the MS, personally). Edited in view of above post

 

[Deleted account 191119001]

BMW have been using these type of tubeless spoked wheels since about 1990, I'm sure they know the stresses and tolerances of them by now

Rims are Behr and they might make them for BMW, however they might not be Behr on the latest WC's, have a lot at your rims

BMW spoked tubeless wheels are reknowned for being v strong

I have seen forks completely twisted and shattered after a crash, however the Behr rimmed wheel is completely intact and not bent

Interesting point and might not be far of the truth, seems a lot of spoked wheels are out of spec, according to others, and this since 2015, maybe they have changed something, can anyone say if their rims are from behr.

http://advrider.com/index.php?threads/tolerance-on-rear-spoke-wheel-for-2016-1200gsa.1139759/

Wonder if BMW made woody take his article about their spoked wheels down.

https://woodyswheelworks.com/BMWTubelessSpokedWheels.html

 

[Warlord]

I'm playing Devils Advocate here for a moment. Even if my answers are not right, it might spark another line of thinking that may lead us to a potential answer...

BMW have been using these type of tubeless spoked wheels since about 1990, I'm sure they know the stresses and tolerances of them by now

Yes they probably do. So what's changed since then?

A) More people are using these machines with spoked wheels on road. (Road tyres have more traction and won't slip)
B) BMW recognise this trend and have added performance upgrades like GSAP which is reported to give a harsh gearchange at times. (jolting sheering force)
C) More people are remapping their bikes for more power and torque. What are Hilltop gains on torque? (more sheering force, may stretch and bend opposite spokes?)
D) BMW may have also changed the specifications of the wheels in the meantime?
- Making them lighter? (thinner spokes)
- Supplier Change? (QC loose spokes?)
- Radius Change? (thinner tyres transferring more energy to the spokes?)

The boxer engine is designed for torque, as torque is perfect for off-road use. The sheering force wouldn't be an issue off-road, as the rear wheel would just spin up.

BMW spoked tubeless wheels are reknowned for being v strong

I have seen forks completely twisted and shattered after a crash, however the Behr rimmed wheel is completely intact and not bent

Yes but a direct impact on the rim is very different from an applied rotational sheering force from the hub. It's completely different.

Spokes provide their strength when under tension. If they are loose or bent or broken, they have no strength.

A fully loaded GSA, with power upgrades (Remap and GSAP), sticky tyres, loose spokes or a rare untrued wheel from factory? A perfect storm maybe?

Have a look at some e-bike forums, as they are now applying electric motors to normal spoked bicycle wheels, they are learning all about torque and how it destroys spoked wheels. I know bicycles have a different spoke layout than motorcycles, but the principle of applied torque is the same.

This is just a quick example:-

https://electricbike.com/forum/foru...much-power-can-a-standard-rim-and-spokes-take

 

[Warlord]

Or the OP just forgot to tighten the caliper bolts up and hasn't told us that.

 

[Mr Bean]

Or the OP just forgot to tighten the caliper bolts up and hasn't told us that.

In one, or someone else forgot to

 

[fred_jb]

From what I have read, the addition of cush rubbers to hubs of chain driven bikes came about at least partly to reduce damage to the wheels, so I think high torque and heavy loads can be damaging.

However, there doesn't seem to have been a long history of spoke failure on BMW shaft drive boxer twins, so if these recent failures are of the wheel itself rather than damage from external sources like loose calipers, then something has to have changed on more recent bikes.

 

[GrinningGSer]

As said before, the OP says he didn’t remove the caliper , but that’s not the same as confirming that the caliper bolts were not already loose . Has the bike ever had its final drive dropped to lubricate splines ? Was leverage applied to the the caliper to force the pistons in during pad change ? Where are you OP and any updates for us ?

 

[Deleted account 220214001]

This is a photo of the rim on my friend's 2017 Ride spec bike. Is this what you guys are looking for or would the BEHR mark be inside?

 

[JohnnyBoxer]

This is a photo of the rim on my friend's 2017 Ride spec bike. Is this what you guys are looking for or would the BEHR mark be inside?

Looks like BMW changed manufacturers of rims, from Behr to some firm called GLM??

This is an older Behr quality wheel, made in Germany