welding disc brake mounts... thoughts and advice

[Woz]

I've done this on a 1995-ish Parkpre Ti Pro Elite.

I made a jig out of an old steel headset spanner, got a Ti disc tab from Paragon, did the tab "maching" myself, then
found a good local welder (experienced and certified in the aerospace industry) to put the disc tab and a cable guide on.

Worked fine......well untill an earlier repair (done by ?) around the BB cracked, so the frame was subsequantly scrapped.
I've got another disc tab for another build - won't hesitate to do the same again.

 

[bren]

Isn't rotor clearance going to be the biggest issue here?

Not really, konas have crap chainstay clearance, a 2.1 tyre is snug, yet I'm running a 185mm disc at the back with no issues.

 

[parkerfresh]

Thank you for the response guys, seeing the pics is a little extra motivation

After looking into it a little further, I think its a relatively simple job, I think disc clearance is an issue if you have crazy snake stays, but I plan to have it done on a kona (just got to find one now!)

There is a price list on the Argos site... Disc mount welding will cost £60 but that doesn't include the price of the mount, I don't know if they can sell me one or I have to source one elsewhere?

I will email them and find out. I plan on keeping the whole build relatively simple and i'll try to be sympathetic when choosing parts, but I will be using this a lot so performance and comfort will be more important than being period correct.

Cheers guys

 

[Rob H]

Re:

I've given this a fair bit of thought for a future project.

Whereabouts are you? There are more frame builders in the UK than you'd expect however they tend to be quite busy, alternatively a competent welder could tig or braise it for you but the frame builder will have a jig to keep everything aligned. You can buy the mounts online for between £5 & £20 just search for frame building supplies or you could make one out of a bit of steel, some chain drilling and an afternoon with a file if you want something a bit more unique. I'll probably go for this one, as I like how it runs up the stay:

http://www.paragonmachineworks.com/cgi- ... key=BK2009

 

[NeilM]

I plan on keeping the whole build relatively simple and i'll try to be sympathetic when choosing parts, but I will be using this a lot so performance and comfort will be more important than being period correct.

Take another look at my Cats Wiskas; I am running it SRAM 2X10 with grip shift and BB7 mechanical calipers. Wheels are Hope hubs with Mavic XC717 rims. There is no reason why you can't use selected modern components on a retro frame, you end up with the best of all worlds.

 

[parkerfresh]

Thanks for the info on the disc mount, I wouldn't mind having a go at making one but I know I won't be able to do as good a job as a purchased mount, plus I don't have a fantastic array of tools yet. I am in Portsmouth (UK), I don't know if there are any frame builders close by? I'm not in a hurry to get this done immediately, I need to source a frame, strip paint, lugs and maybe some guides, then I've got to buy EVERYTHING else.

I've got my 09 rockhopper to keep me going until this project is done, and while I dislike it more every time I look at it, it will do until this project is finished.

Oh, and the cats wiskas is great, I'm not sure what components to run as of yet, I know i'll probably run a modern SID fork, probably hope disc hubs, probably 1 x 10 gearing... Was thinking about maybe putting on some profile cranks? I'll probably change my mind loads though. Been sniffing out some old hope brakes on the bay but there's not a great selection at the minute.

 

[bren]

Hope brakes tend to command silly prices on fleabay, better off waiting for a good set to appear on the for sale 1998 on forum on here if you're not in a hurry.

 

[fignon1989]

I had Mercian weld a disk tab on the rear of what turned out to be a Saracen frame I got from Dentons Cycles for next to no money. If you look at the lets see some Saracen thread its the blue and white frames with the S removed from the rear of the tube going through the seat tube. I think some one called "big Dave" or some thing like that has a couple of the same frames. I cut and filed the canti studs off (easy to get right but could go horribly wrong!) and the end result is a clean looking frame. I did not bother with the bracing tube and have not had a problem. I took the wheel and disk brake to Mercain for them to line up the tab. Just to show how good Mercians work was the end result was so in line I did not need to use any washers to line up the Hope C2 brake, it was spot on!! To save money at the time I did not have a paint job done (very expensive at Mercain but value for money for the quality) and just tuched in the paint with Humbrol model paint. It has now had a powder coat in matte black. It spent quite a few years geared but now has been singled speeded. It is a very nice bike to ride and whilst I would think twice about having the work done on "classic" retro frame, if you want a rider rather than a show pony it is well worth getting the work done by some one who knows what they are doing. If you look at Mercians site they quote £65.00 for the job and do require the brake and wheel.

 

[02gf74]

Re: Re:

but the frame builder will have a jig to keep everything aligned.

the jig could be a hub with disc rotor fitted and a brake calliper fitted to the tab with brake applied using an elastic band, include a couple of shims to allow for any adjustment in case there is any movement of the tab during welding..

a couple of tack welds either side of the disc brake tab should keep it in place for the final welding

you may want to include a brace between the chain and seat stays - useful to strengthen non-disc frames.

 

[parkerfresh]

I was thinking the same... If the hub and rotor are in the frame and the calliper is bolted to the mount, once the calliper is mated to the rotor, everything should line up correctly (in theory) and can be tacked? I will still get a professional to do this as its not worth messing about and I will definitely be getting a brace put in too.

What are the advantages/disadvantages of a small rotor compared to a large? I will get more clearance with a small rotor, but will there be more stress/forces put on the frame? Is a larger rotor better?