Topic: Rim weld, flat spots & wheel balance

[lordmoonpie]

This may seem like a silly question but I'm gonn aput it out there anyway. I just took delivery of my new rear race rim - light weight alloy flanged DID rim all laced up with my RC181 replica hub. However, I noticed that where the hoop of the rim has been welded up inot a circle, the outer lip of the rim on both sides has a very very slight flat spot. You notice it when spinning the wheel on a spindle - all good and then a little tiny blip at that point.

My thinking is that this is not a good thing for a race bike and I need to send it back. It doesn't see buckled as such, just a little flat spot.

Any views?

[Sam Green Racing]

Where did you buy the rim and who laced it up ? AND, when are you going to phone me back regarding my stickers.

Sam.

[turboguzzi]

they are never perfect at the welding, but some can be worse than others.....

[lordmoonpie]

The rim came from Phil Denton Engineering - Phil is  perfectionist so I've asked his opinion on it before I send it back. He'll sort something out of it needs it, his service is top drawer.

Oh yeah - got to ring you Sam, tonight I hope if I get a moment's peace!! 

[NickO]

I'm wondering if the imperfection is big enough to allow the tyre to deform "into" the flat-spot, as you describe it as "very, very slight".

There is probably more natural run-out on any given "perfectly fitted" tyre if you were to able to measure it accurately enough, such that this flat-spot has no effect on the actual O/D of the tyre at this point?

it would be an interesting exercise to measure it against a perfect rim/tyre and although I have no prior knowledge/experience, I would doubt it would make any difference!

[MCRider]

I was raised to gauge roundness on the area where the bead sits in the rim, not on any outside edge surface. The rim is usually serrated in there. If that's flat at the weld, you may feel it. If its an outside edge I don't worry. But i don't race either. And I am a pure amateur and defer to anyone who knows better.

Pretty much just curious to know what you decide.

[simon#42]

I was raised to gauge roundness on the area where the bead sits in the rim, not on any outside edge surface. The rim is usually serrated in there. If that's flat at the weld, you may feel it. If its an outside edge I don't worry. But i don't race either. And I am a pure amateur and defer to anyone who knows better.

Pretty much just curious to know what you decide.

you are right MCRider the crucial area is where the bead sits , i have a few DID rims in the garage simon , when i looked at them closely these where pretty much as you described yours but i have used all of them in the past with no problems . TG was right as well , some were better than others .

[turboguzzi]

Just had a look at two rims i have in the balcony, (bought for an aborted RD350 racer project). A Spanish 1.85" Akront is close to perfection, had a hard time FINDING the weld....

The 2.15" Borrani has a some heavy filing in the weld area but still pretty good. Worst I've seen is the 3" unmarked rim i am using in the rear of the 500, pretty bad flat looking spot but tire runs true, so go figure, guess it's really the tire contact area that counts.

TG

[lordmoonpie]

Thanks guys - I guess I'm just getting paranoid in my old age
I looked at the front rim last night too - it's the same rim type (Record not DID it turns out - see I told you I'm getting old). It has the same issue. Crucially though, the shoulder where the tyre sits seems to have no run out at all in the same place so I think I'm good to go with this rim and I'll keep it. Shame it got marked on the rim edge during transit but that's cosmetic not functional so I can live with it.

Thanks for the opinions and experiences as ever guys - darn I love this forum

Next on the shopping list is a pair of shocks and then I can start frame mock-up and some pictures for you guys at long last.....ooooo......beaten aluminium fairing tooo 

[754]

  If you Dont use a dial indicator for truing, it wont drive you so nuts.. get it as good as you can, THEN check with a dial.
 Pretty hard to get a rolled rim perfect at the joint..  Your rim trueness can be looked at as a mean average..., meaning over 58 inches of circumference, if its out in a 1 inch portion, it probably wont be something that will trow out the tire..

[lordmoonpie]

Wise words 754 - it looks like small beer indeed when you put it like that...