Disc conversion on a non disc bike??

[Jay_Jay]

I've got a Specialized Stumpjumber FS with good old rim brakes, I'm considering a disc conversion.

I'll obviously need new hubs for the discs themselves, but the frame/forks don't have bosses for calipers.

The frame is one the M variants ( a weird mix of alloy and ceramic ) so I don't think welding bosses on is an option either.

Has anyone tried a conversion along these lines? any suggestions?, or don't bother!?

All feedback welcome.

Thanks

Justin

 

[Hecubus]

Originally posted by Jay_Jay
I've got a Specialized Stumpjumber FS with good old rim brakes, I'm considering a disc conversion.

I'll obviously need new hubs for the discs themselves, but the frame/forks don't have bosses for calipers.

The frame is one the M variants ( a weird mix of alloy and ceramic ) so I don't think welding bosses on is an option either.

Has anyone tried a conversion along these lines? any suggestions?, or don't bother!?

All feedback welcome.

Thanks

Justin

If your frame and fork don't have the mounts I'm assuming you're bike is rather old, possibly pre 1999. There is absolutely nothing you can do about the fork except getting a new one. I think there is this adapter that attaches to the chainstay to allow for a rear disc but its really not worth it. You can't just weld the tabs on. If you really want discs its probably time you upgrade your bike or just live with what you have.

 

[ireman_1]

Originally posted by Hecubus
If your frame and fork don't have the mounts I'm assuming you're bike is rather old, possibly pre 1999. There is absolutely nothing you can do about the fork except getting a new one. I think there is this adapter that attaches to the chainstay to allow for a rear disc but its really not worth it. You can't just weld the tabs on. If you really want discs its probably time you upgrade your bike or just live with what you have.

Exactly like Hecubus said, none of the options are all that great. You could get a new fork for the front and an "adapter" for the rear (it bolts to the drop-out and left brake boss). I've heard of issues with those set-ups (the weight penalty being the least one to worry about). IMHO: There are plenty of folks running disc front and rim rear these days and that seems a reasonable option for a lot of riding. Most of your stopping power should be used in the front anyways so having a "stronger" brake on the front makes some sense. You could have the avid mechanicals on the front for cheap to (don't have to get new levers, just the hub and fork).

Who doesn't love buying new forks?

You can get good rim brake set-ups to work really damn well for most every condition (except wet and mud). Ceramic coated rims and abrasive pads worked great for me (with XT V's) until I "gave in" and went disc. With that option you are just getting new rims and pads (maybe levers?).

Have fun!

K.

 

[Jay_Jay]

Originally posted by ireman_1
Exactly like Hecubus said, none of the options are all that great. You could get a new fork for the front and an "adapter" for the rear (it bolts to the drop-out and left brake boss). I've heard of issues with those set-ups (the weight penalty being the least one to worry about). IMHO: There are plenty of folks running disc front and rim rear these days and that seems a reasonable option for a lot of riding. Most of your stopping power should be used in the front anyways so having a "stronger" brake on the front makes some sense. You could have the avid mechanicals on the front for cheap to (don't have to get new levers, just the hub and fork).

Who doesn't love buying new forks?

You can get good rim brake set-ups to work really damn well for most every condition (except wet and mud). Ceramic coated rims and abrasive pads worked great for me (with XT V's) until I "gave in" and went disc. With that option you are just getting new rims and pads (maybe levers?).

Have fun!

K.

Thanks for your replies, I'd pretty much come to the same conclusion, I may look into a front disc and maybe a hydraulic rim brake on the rear, but as always you end buying more than you expect (levers, shifters, hubs, forks........).

I guess if you can lock the front wheel then you've got enough power, but the UK is known for it's variable weather & I think a disc will be more consistent. A trip to ebay...

Cheers

Justin

 

[hedgehog]

my 2k specialized fsr came with Hayes hydraulics, it has the adapter and I have never had any problems with it. It looks odd but other than that no issues.

 

[cd667]

Maguras are very nearly as good as discs, will work forever with minimal adjustment/maintenance, and are a sight cheaper than a new frame, fork and hubs. Just a thought.

 

[dabac]

.. I'm considering a disc conversion....I'll obviously need new hubs for the discs themselves,

You don't have to replace the hubs, look at http://www.firstprinciples.ca/

 

[willtsmith]

You don't have to replace the hubs, look at http://www.firstprinciples.ca/

Only if you REALLY, REALLY like your wheel components. Because you will have to rebuild it using these things. A new wheel with disc flanges will probably cost you $30-$40 at the bottom end.

 

[Conniebiker]

Since you have a matrix frame welding is unlikely(though there may be a process the mfg would know of) and unpractical.
Doing a nose-only setup is perfectly valid. The front is where you need the best reliability and control. A lot of jumpers and stunt riders still run this configuration.
A fork that does not have a tab on it is in my opinon behind the technological generation. Even the very cheapest forks now have tabs, and a mid range newer fork will out perform and easily take off a pound or two from the one you have now. That alone will help the feel of your ride. Add to it the front disc and you will have a whole new feeling bike.

 

[jcueto]

A couple of years ago I convert a 1999 Stumpjumper FSR XC comp from V brakes to disks. I promise not to do that again.

The adaptor for the rear brake was difficult to find, I need to change the front fork and the whole wheels (I cannot find disk hubs with the same numbers of spokes). I ended with a lot of great components used for sale and a much more expended in parts than aticipated. The result was a heavier bike wich brake gooood!!.

I really love disk brakes, by far are much better than V brakes, however the conversion not worth it. I ended selling the bike and buying one with disk brakes already.

 

[alcazar]

I've done this on a Raleigh Titanium MTB frame, no less!

It involved a LOT of research, and even more goodwill.

I first contacted Raleigh and spoke to an enthusiastic guy in what used to be Raleigh Special Products. He informed me that my frame HAD BEEN available, the year after mine was made, with disc mounts.
He searched out, and sent me, free of charge, working drawings for the non-drive side drop out and disc mount.
He also gave me the name and address of a company in Chilwell, Nottingham, which made the original dropouts for Raleigh, on a very specialised wire cutting machine.

I then contacted them, only to find the manager was another bike nut!

After a visit and talking bikes for about an hour, he agreed to make me a new dropout to my drawing, using some of the Titanium he had left from when the OE ones were made. Cheap too!

Two weeks later, I had my dropout/disc mount.

Yellow Pages helped me find a welder competent in Titanium, and I made up a jig to hold the new dropout in place once he'd cut off the old one. He welded it up, and the bike is going strong now, with Hope XC's front and rear.

Alcazar