Originally Posted by Snowy
Hey Woody, how many times can you hammer a rim straight in the same spot?
I know that's completely subjective and speculative, but...it is the F800 forum. Subjective speculation is what we do.
I've had enough dings where you can clearly see about 50mm to 80mm of the bead. If I deflate the tyre, and sit the wheel on a large flat wooden surface (my work bench) then use the plastic faced hammer and beat the bent section down until it's more or less parallel again.
I've done this enough that there isn't a 200mm section of rim on either side that hasn't been straightened, and some sections have had 2 or 3 goes and have obviously work hardened as they get harder to straighten. It's no longer officially "round" in any real sense of the word. Octagonal is the term I use.
So what's the professional's advice? Am I dicing with death and dismemberment? Or will it crack and show obvious signs of abuse before things go bad?
I realise the width of the rim is the prime culprit in the ease in which they ding. How come I can't get Excels or others in anything wider than 1.6 inch? SM Pro do a 1.85 I think, but trying to get one locally has proved a quest like the search for the Holy Grail. People advertise that they do them, but I've commissioned 2 wheel builds, given them credit card details, and never heard from them again.
Technically you should use heat and a press to straighten the rim out instead of hammering. Unless you get it really close to straight, we use the runout of +/- 0.010", then the rim will continue to be more likely to bend further in the area that is already bent. Hammering it out is really only a short term fix to get the bike home or to next destination where can be repaired or replaced. The rim is far more likely to crack when you don't straighten with proper techniques. If you continue to hammer out and bend the rim, it will eventually crack, still the wheel will not disintegrate because you have the spokes/nipples holding in place and tire around it.
An interesting thing about the stock Behr rim, is that because it is so soft, it actually has been less likely to crack when repaired then other rims, but more likely to bend again because of the attributes of the aluminum used to manufacture it.
As you mentioned there is a solution, going to a narrower and higher quality rim. If you want to be able to use your stock spokes and nipples and stock lace pattern, then the two options are the Excel 21x1.85($290) and the DID DirtStar 21x1.85($199), These rims will significantly decrease likelihood of rim bending and do little to change on-road performance.
If doing more aggressive off-road riding, and want the 21x1.60 A60 rim($199 + drilling & spokes), you would need to drill the rim or have drilled for a x3/x2 lace pattern, and increase the length and angle of spoke on one side to make it work with the stock hub. Otherwise if wanted to go with the 21x1.60($214), but did not want to swap out the spokes/nipples, or change lace pattern, we can get the double signature 7000 series Excel custom drilled and anodized in black.
Excel does not yet offer an off the shelf available to everyone 21x1.85 Euro drilled black rim because they have seen the market and specialty in dirtbike rims and there are really no dirtbikes that require a 21x1.85" rim and none that have the Euro lace pattern. We do foresee that they will have such a rim more widely available in the future, but for now we have them custom made to our specs either directly from Excel or by anodizing silver ones that we purchase. Supply and demand.
The DID Dirtstar rim, outside of the one that has been available from KTM off of the SuperEnduro has only become more widely available from DID in the past 3-4 months as they have seen an increased market for it and why available for less expensive price, although KTM still retails the same rim for $295, that DID retails for $199.
I do not know about the SM Pro rim, it certainly is not as high a quality as the Excel or DID and do make sure that it is Euro drilled if you plan on re-using stock spokes and nipples.
Hope that clarifies some things.
(Woody is in Moab at the GS Trophy & Adventure Rider Challenge this week, check out here: http://www.adventureriderchallenge.com/