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'89 and '95 R100RT disc brake rotors (and EBC replacements)

S

Scarletswirl

New member
My recently rebuilt '89 R100RT (42K miles) shows symptoms of uneven or warped dic rotors. Checked thickness with micrometer. Above 4 mm, but uneven. To compare, I checked my '95, with 20K original miles. 3.88 mm, but very uniform. Just as a reference, Haynes says the spec is 4 mm. I can't believe 20K miles is enough to wear out brake disc rotors, and it doesn't make sense that the '89, with double the miles has thicker rotors. Is anyone aware of any switch in the rotor thickness through the model years?

By the way, Snowbum says manufacturers tend to be too conservative with thickness specs and slightly undersized rotors should not be a problem. The '95 bike brakes fine, so I'm not overly concerned, just curious.

Second question, more important. Since the original rotors are near unobtainable and expensive, I went with EBC Pro Lite for the replacement and they just came in. Checked thickness, very uniform, but 5 mm instead of 4. Has anyone tried them? Does the added thickness cause problems, i.e. will it even fit in between the pads? I double checked and they are the right part numbers, but as I remember, the original ones were a tight squeeze already. Snowbum shows an EBC based conversion, but it doesn't use the original calipers, so the effect of the extra thickness is not discussed in the article.

Thanks to all,
Marc
 
For what it's worth, I found my answers

Today I removed the old rotors from the '89. On the hub side that faces the wheel (invisible until you disassemble it) it says "Min .14 in". 0.14 inches is about 3.5 mm, so Clymer's 4 mm value is inaccurate and at 3.88 mm, my '95 is in spec. One problem solved.

As far as fitting a 5 mm thick rotor where a 4 mm rotor used to be, the jury is still out, but I managed to spread both calipers enough to fit a 6 mm (nominal) piece of plywood in there, with some persuasion. The pads are near-new, so new pads shouldn't make a big difference. The actual thickness of the wood is more like 5.8 mm, and even allowing for some compression it will still be 5 point something. And as long as it's more than 5, it SHOULD work.

I'll post again with the final verdict.

Marc
 
Scarletswirl said:
My recently rebuilt '89 R100RT (42K miles) shows symptoms of uneven or warped dic rotors. Checked thickness with micrometer. Above 4 mm, but uneven. To compare, I checked my '95, with 20K original miles. 3.88 mm, but very uniform. Just as a reference, Haynes says the spec is 4 mm. I can't believe 20K miles is enough to wear out brake disc rotors, and it doesn't make sense that the '89, with double the miles has thicker rotors. Is anyone aware of any switch in the rotor thickness through the model years?

By the way, Snowbum says manufacturers tend to be too conservative with thickness specs and slightly undersized rotors should not be a problem. The '95 bike brakes fine, so I'm not overly concerned, just curious.

Second question, more important. Since the original rotors are near unobtainable and expensive, I went with EBC Pro Lite for the replacement and they just came in. Checked thickness, very uniform, but 5 mm instead of 4. Has anyone tried them? Does the added thickness cause problems, i.e. will it even fit in between the pads? I double checked and they are the right part numbers, but as I remember, the original ones were a tight squeeze already. Snowbum shows an EBC based conversion, but it doesn't use the original calipers, so the effect of the extra thickness is not discussed in the article.

Thanks to all,
Marc
Click to expand...

I went with EBC Pro-Lite rotors when the originals on my '93 R100RT warped. They worked fine and my only complaint was that some of the hardware wasn't plated to resist rust. I think it was the floating clips but I don't have the bike anymore to confirm.
 
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