Mac Motor design flaw rotor bolt depth?

[kudos]

Just the other day I read a post by someone saying they had pushed metal shards into their new motor from the rotor bolts screwing through the case cover.

EDIT: Found it http://endless-sphere.com/forums/viewtopic.php?f=3&t=42192

Even knowing this and trying my best to measure and checking rotor bolt length which appears to be a standard length. I did exactly the same.

I took the side off and fished all the shards out best I could. I took my time to try and ensure there was nothing left. I've powered it up for the first time and it appears to spin with no grinding.

I just don't understand, surely this must happen to everyone who attaches a rotor? Or am I missing something?

I've searched but I can't seem to find any 'short' rotor bolts?

 

[cal3thousand]

Did you run a spacer on there?

 

[kudos]

If you mean a rotor spacer then no, why would I?

I do actually have some rotor spacers as it happens, if I'd have known what was going to happen, I would have put some on the outside of the rotor to prevent the rotor bolts from descending quite so far.

Kudos

 

[atom1025]

Yup the spacer is needed anyhow, without a spacer most calipers will rub the can. My bb5 clears the can by 2mm only with a 2.5mm spacer.

 

[el_walto]

I had the same problem, i used a spacer from ebikes.ca, i needed a spacer anyways for it to align correctly.

 

[kudos]

Did you guys put your spacer between the case and the rotor then?

 

[cal3thousand]

Did you guys put your spacer between the case and the rotor then?

Yes

 

[neptronix]

I forget how much spacing i used, but i do remember needing 1-2mm of spacers to get the rotor on my early 2011's MAC

 

[mvly]

If I remember correctly, ebikessf sells shorter bolts for rotor mounting on the bmc.

http://www.ebikessf.com/node/168

I guess it is the same for the MAC.

You would need shorter bolt.

 

[neptronix]

You shouldn't need a shorter bolt if you're using spacers, fyi.

 

[el_walto]

I'd consider it a flaw, especially since it's hard to find bolts shorter than 6mm. You could probably just use some washers, but i used the part form here http://ebikes.ca/store/store_connectors.php $7 plus a bunch of shipping

 

[kudos]

I'm with el_walto here, as far as I'm aware this is the only motor where you can't use standard rotor bolts.

What narks me more than anything else, is that there simply isn't any way for you to know about this problem.

The kits come with no instructions. There is nothing on emissions-free website to warn you and Paul didn't mention it to me when I ordered the disc brake only wheel rim???

This must happen to everyone who buys this motor for the first time ???

Kudos

 

[kudos]

Yup the spacer is needed anyhow, without a spacer most calipers will rub the can. My bb5 clears the can by 2mm only with a 2.5mm spacer.

atom, as it happens on my commuter I have a BB5 up front but still running the original brake on the rear. I have BB7's on my new build which isn't up and running yet but after your post here I've ordered another BB5 for the rear.

I have 1mm and 2mm hope rotor spacers, but not half mil. You said you used a 2.5mm spacer, where did you get this from ?

Scratch that - just noticed the one from ebikes.ca is 2.5mm

Cheers,
Kudos

 

[atom1025]

A ghetto fab way of doing it is to use an old rotor and cut/grind/sand/ or file it down to make a spacer just like ebikes.ca has.

 

[kudos]

Ah yes that's a good idea in a pinch atom.

I priced up that 2.5m spacer from ebikes.ca: 7$ for the spacer seemed a bit steep, but then when you add postage of $55.30 which is a total joke for something that weighs as much as an envelope it's not an option.

CCR do these hope rotor spacers for £1.66 delivered: http://www.chainreactioncycles.com/Models.aspx?ModelID=3288 They come in 1mm and 2mm.

I've used a 2mm and a 1mm to make 3mm in total, looks like I can fit my original caliper on now, though haven't had a chance to lock everything down to be sure.

Kudos

 

[miuan]

I tend to use bigger rotors than 6"/160mm so my MAC is spacerless
The BPMs barely need any spacers as they are. Much depends on the caliper.
Hayes MX4 are quite narrow and work reasonably well, if not as well as Avids.

 

[kudos]

miuan - I like the idea of using bigger rotors, I'm putting 203mm roors on my new build actually....but....that doesn't change the fact that if you put a rotor on the mac without a spacer, you can't use standard rotor bolts, they will screw right through the case.

So what rotor bolts do you use and where did you get them from ?

Cheers,
Kudos

 

[miuan]

I just add hardware store spacers on top of the rotor if needed.

 

[kudos]

Ah I see, do you mean individual washers under each bolt or does your hardware store actually sell proper rotor spacers ?

Kudos

 

[miuan]

Ah I see, do you mean individual washers under each bolt or does your hardware store actually sell proper rotor spacers ?

Kudos

Sorry for my english, sure I meant standard washers.

 

[kudos]

I'm having a switch around of my motors on my bikes and I've run into the rotor spacing issue again.

I need to attach the rotor to my Mac either directly or with a 1mm spacer.

As per this thread, normal rotor bolts are too long and push through the casing.

I have followed the links in this thread but I can't find the short rotors bolts for bmc motor on the grin cyclery store, I have emailed them to see if they still sell them.

Does anyone know of anywhere else that sells short rotor bolts?

If I can't find any i'll have to use spacer washers on each bolt I suppose.....

Kudos

Edit: it just occurred to me that I can use rotor spacers on both sides of the rotor thereby negating the need for shorter bolts! Doh....

 

[spinningmagnets]

Just as a point of reference, I drilled the M5/5mm X 0.80 threaded disc brake holes all the way through with a 4mm pilot bit, and then threaded the entire length. Turns out the side plate is 9mm deep in that spot.

 

[DAND214]

Shorter bolts is no problem.
McMastercarr sells the 100 for the same price as buy 6 rotor bolts. Allen or torquex button head screws are easy to get.

Dan