Rotors & Tire Balancing

[cabreco]

As I posted before I am putting on new E3 Dunlops on my 84 using the rims from my donor bike. Now the donor bikes rotors have over 70K miles on them & are thinner than the ones on my bike (I only have 15K on my bike). This being the case I will be swapping the rotors once the new E3's come back mounted.

 

My question is will swapping the rotors AFTER I have the new tires balanced significantly affect the tire balancing???

[Daitan]

I would say yes. And if it is possible talk to the bike shop and see if you can bring them down and change them out before they balance them. That way the better rotors are balanced with the new tires. Most bike shops should be accommodating. :080402gudl_prv:

[dingy]

As I posted before I am putting on new E3 Dunlops on my 84 using the rims from my donor bike. Now the donor bikes rotors have over 70K miles on them & are thinner than the ones on my bike (I only have 15K on my bike). This being the case I will be swapping the rotors once the new E3's come back mounted.

 

My question is will swapping the rotors AFTER I have the new tires balanced significantly affect the tire balancing???

 

 

I would say no, they should not effect balance signifigantly.

Rotors are held in place very close tolerance with the releif cut in the rim that centers the rotor to the rim. This keeps rotor center concentric to the rim center.

Rotor wear should be very even radially around face of rotor, so there should be no weight difference there.

Now, the 83-85 rotors may have an issue due to the ventilation in the rotor edges. There could be uneven contaminents built up in the pockets that would effect balance. But this weight out of balance potential is much closer to the rotational axis of the wheel than the tire, so the added weight would not effect the balance condition as much if a similar weight were put farther away from the centerline of rotation.

I have swapped rotors numerous times during my front brake experiments with no noticable changes.

Then I could be wrong !!

Gary

[cabreco]

...Then I could be wrong !!

 

 

Gary

 

LOL! After all that!

 

Gary since you've swapped them out before, would you happen to know off hand the torque specs for them??

[Yammer Dan]

14 ft. lb.

 

And I don't think it will mess with balance enough to be a concern if rotors are in good shape.

[cimmer]

I would have them balanced with the rotors you will be running on the bike. There can be minor differences in each rotor as there are in tires. Might not be much and might not be real noticeable but they could easily affect tire life in the long term as they are a major part of the rotational mass you are trying to balance out.

Just my opinion,

Rick F.

[dingy]

I'm not saying not to have them balanced. If the voices in your head are undecided, get it done.

 

Unless you get them high speed balanced, I really doubt it will make any difference. What I have seen used a lot is the type of balancer that the axle sets on a pair of pillars and you repeatedly spin the tire and add weights till it stops at a random point many times in a row. This is a very low tech way of balancing. Low cost and many people have them, but not highly accurate.

 

Yammer was correct on rotor screw torque. Be careful taking them out of wheel. They are cheap, soft steel screws and have been known to strip head out.

 

Picture attached of pockets in MKI rotors I mentioned earlier, crappy picture but you can make them out.

 

I have a pretty good set of MKI rotors They measure about 8.25mm, New ones are 8.5mm so these have very little wear. There is some minor surface rust that will clean up easily. They aren't grooved very much. PM me if interested. 2nd picture is of one rotor. Also have the rear one from same bike. I can send you a few spare screws if you get rotors.

Gary

[Yammer Dan]

I change my own tires and thats the only nethod of balancing I've ever used. Two corner cinderblocks with the groove in the end work great.

Course as slow as I run it probally wouldn't make any difference.

[cabreco]

I'm not saying not to have them balanced. If the voices in your head are undecided, get it done.

 

Well I spoke to the service dept at the Yammy dealer & he confirmed that it won't make a difference. (basically he said exactly what you posted)

 

Yammer was correct on rotor screw torque. Be careful taking them out of wheel. They are cheap, soft steel screws and have been known to strip head out.

 

Picture attached of pockets in MKI rotors I mentioned earlier, crappy picture but you can make them out.

I have them soaking now with a 50/50 mix of acetone & automatic transmission fluid so that they will not fight me. I cleaned up the rims I will run my Dremel through those hole to clean them up.

 

 

I have a pretty good set of MKI rotors They measure about 8.25mm, New ones are 8.5mm so these have very little wear. There is some minor surface rust that will clean up easily. They aren't grooved very much. PM me if interested. 2nd picture is of one rotor. Also have the rear one from same bike. I can send you a few spare screws if you get rotors.

Gary

 

I appreciate the offer but like I said my bike only has 15K original miles & the rotors are in really nice shape. The parts bike rotors aren't bad either but they have over 60K miles on them & look more worn than my bikes.

 

I appreciate the help guys!

[MiCarl]

What I have seen used a lot is the type of balancer that the axle sets on a pair of pillars and you repeatedly spin the tire and add weights till it stops at a random point many times in a row. This is a very low tech way of balancing. Low cost and many people have them, but not highly accurate.

 

Gary, as much as I hate to disagree with you I must on this statement. I use this type of balancer in my shop and I can easily find less than 5g imbalance. Since 5g is the lightest weight I've seen it is more than good enough.

 

Spin balancing may be theoretically more accurate, but if you can't get the weights it's pointless. Furthermore if the spin balancer isn't kept calibrated it'll give incorrect results. So long as gravity doesn't move around mine is repeatable.

 

One nice thing about spin balancers is they tell exactly how much weight to use instead of trail and error. I've done it often enough with the one I have I can usually get within 10 grams just by how it feels. Considering set up time on a spin balancer I may be just as quick as spin balancing.

 

Where high speed spin balancing is essential is a dynamic balance where both the inside and outside of the wheel are balanced to prevent wobble. Important on car and truck tires but not used on motorcycles.

 

Now I have to state that my balancer has its own bearings and axle. If you're putting your axle through the wheel and hanging it on a couple cinder blocks the condition of the bearings and drag from the seals will affect your results. There are ways to overcome that too, but time consuming.

 

By the way, you'd have to really mess with a rotor to change its balance enough to show up as 5g way out at the rim. That's why they just don't matter.

[dingy]

Gary, as much as I hate to disagree with you I must on this statement. I use this type of balancer in my shop and I can easily find less than 5g imbalance. Since 5g is the lightest weight I've seen it is more than good enough.

 

 

Give me a break Carl, it sounded like I actually knew what I was talking about. Yamaha dealer even agreed. !!

 

 

With proper equipment and an experienced hand, much better results are achievable.

 

Gary

[Yammer Dan]

With proper equipment and an experienced hand, much better results are achievable.

 

What doesn't that apply to?? I've seen guys that were overwhelmed by the cinderblocks....

[Venturous Randy]

I have used the axle and jack stand method many times and always had good success. If the bearings or axle don't work well, you have a different problem.

I worked at Superior Wheels in the Quality Department for awhile where aluminum wheels were made for GM and others. We had several wheel balancers and calibration was routinely checked. What I have found from local tire suppliers is they can dynamically balance a tire and then loosen the holding fixture and rotate the wheel/tire combo 180 degrees and it will get a different reading. That tells me that their equipment is not repeatable.

RandyA