Blackburn Rack Bending
 

Looking for a little help a whether these racks can be bent without damage. I purchased this Blackburn rack and it's from a 22.5" frame. I'm putting it on a 21" frame and the seat stay section of the rack is too wide for my frame. I need to reduce the width about 5-7mm. Anyone ever bend one of these with luck? Is there anything special I should do before attempting to vice them in a bit? Would heating over a flame and bending while the rack is warm lessen the chance of breakage?
Thanks to all in advance.

the difference between annealing and melting aluminum is small .
and just warm is meaningless , annealing metals happens at about the temperature, they glow
hard to see when that is reached but in near dark,


there are other racks with adjustable stainless steel struts ,
copies of the older blackburn racks that may fit better for your needs.

Thank you. Are you saying it's a bad idea to try and bend those fork stay attachments inward 5-7mm (2.5-3.5mm each) without proper annealing?

Forgive me if I'm being really stupid here but is it possible to use slightly longer bolts and just space out the 5-7mm with a few washers?

+1 Use a valve stem nut on each side.

Brad

Not at all. Appreciate the comment.
Right now the rack seat stay attachments line up with the center of the seat stay tubes. I need them on the inside of the stays to attach them to the braze-on's. I need to move them together to get them to bolt on.

How much money do you have in the rack? If my eyes aren't fooling me, those struts appears to be solid aluminum. That alone will make them much easier to bend than if they were tubular. Basically, if you don't have a ton of money in it, I'd go ahead and try to bend it. You don't have much to lose. Worst case it breaks and you buy a new, better designed, rack that will fit without issue.

I wouldn't bother heating the aluminum. If it's heat treated aluminum, you'll ruin the heat treatment if you get it hot enough to make a difference. If it's not heat treated, it'll bend readily without heat. Most people caution about bending aluminum because frames are all heat treated to a T6 temper or higher. At that temper, aluminum won't bend far before it cracks. At T0, 6061 bends very easily.

I have bent Blackburn racks to fit, but bending is going to be problematic, as you will need a double bend to make the ends parallel to the braze-ons and you don't have a lot of length to deal with. You could also ignore the braze-on mounts and use a P clip or get a rack that will fit properly and resell that one.

Blackburn racks are all made from solid aluminum rod and will withstand bending.

just wonder what happens with out any shop classes in schools ? non shade tree mechanical savvy generations..

Thanks to all. I'll try the double bend doing the tips first. Ill go slow and if it doesn't look like its going to go well, I'll stop.

Bruce .. just use soft jaws , wood in the vise, etc. you dont want sharp nicks in aluminum .

Bending 3.5mm per side is nothing for these racks. Most bikes will have to have these Blackburn racks bent a little to fit. Contact Blackburn if you want the most cautious answer and I'm sure they will say it's OK.

Why not fit them to the outside of your eyelets? Just spread the legs out 3mm and they will spring back, no ned to permanently bend them . I think I did this with one of my racks, many years ago and it is still working.

The discussion is about the top two attachment points that run to the seat stays.

I've used spacers mostly to clear the brake on this install.

Soft jaws was something I would have overlooked. Great input and thanks. The rails are solid aluminum so it's good to hear positive comments about bending. I plan on attempting this over the next month and will post pictures upon completion.

I have 2 old Blackburn racks and have used them on a number of different bikes. Each time I would make some bends to customize to the new frame, both to spread/compress or level the rack. I have never had any issues at all. The rack I am currently using on my commuting bike has ~ 30 years use. 5-7 mm is nothing - go for it. Remember - slow and steady pressure is what you are after.

Good luck

Just got pretty much the same rack, and have the same issue, so I am very curious as to how it worked.

You may not get an answer as this is a zombie thread from 2013

Use a long bolt and spacers. Blackburn racks used to come with aluminum spacers for such purposes.

Doing so will put some leverage on the braze on, and the bolt, if not completely tight, will wiggle in the braze on, loosening more and doing damage. Whenever i need to space out a rack, I install a long bolt from the inside out, so it is screwed tightly against the braze on. For extra piece of mind, fasten a nut from the other side. Then you have a length of bolt really securely attached. Use spacers or washers, then the rack, then a washer and a nut.

Here a bolt with a standard external hex head (for a crecent wrench), not an internal hex head used more commonly today, is your friend. The head is lower profile (to minimize clearance issues this set up can cause) and easier to tighten when the better access is from the side.

That's a very strong rack. I've installed dozens of them, and have "tweaked" them a little here and there with no ill-effect. Still, others have suggested to simply use longer mounting screws and a spacer of some kind. I would leave a millimeter or two of space to allow the arms that attach to the seat tubes to suck in a little, creating some outward force to the heads of the screws, which will help with them ever loosening while on tour.

Yes, but welded aluminum that has been post-weld heat-treated. I believe as well, that its 6061 aluminum so cold-bending would likely crack it, or start a fatigue cracking process. I would suggest just using spacers. Sounds like a few mm on each side. Use a good quality bolt. I have a Blackburn and most of the weight is supported by the seat stay eyelets, so the longer bolt plus spacers should be just fine.

If you had to bend 6061, you would need to heat it with a torch.

Ahhhh. A zombie thread! I was sucked in!