I have a frame built out of True Temper Platinum OX (the USA 853 equivalent), the frame has the standard chainstay and seatstay bridges. Over the Christmas period I am going to send the frame to Bob Jackson in Leeds for a re-spray.

While its stripped of the paint I was thinking of getting them to move the two bridges closer to the BB and seat tube area to gain slightly more tyre clearance (the frame has plenty of width for fatter tyres but not for the extra depth they create). They have said that they can do this no problem (no technical problem) as they will cut and grind the old ones off and re-weld the new ones on.

As it’s a steel frame I’m not worried about the strength of the steel to cope with being re-welded, that’s fine. But will it affect the frames structural integrity, as I know the bridges are there for a reason, but I’m moving them, not removing them, I’m only talking about an inch, but how much of an effect will on the strength of the frame (btw this is a XC frame not a hardcore hardtail – and wont be subjected to drops, jumps etc).

Can anybody help and thanks in advance.

Done this myself on a road frame (brazed not welded) to convert it for CX without problem. Can’t see that it’s going to have any effect whatsoever.

Considering that Bob Jackson are one of the oldest and most respected frame builders in the country, I’d say that if they think it’s OK then it is.

Totally agree with you about Bob J experience but it was a yes, yes, yes from them, just pick from the price list. Which is fine but Bob J do specialise in road bikes.

So I was asking the question on here as in know there are certain guys who frequent this forum who specislise in mountain bikes. So a second opinion is never a bad thing.

It’s a very expensive frame so I don’t want to mess this up.

*** all I’d have though – if it’s a similar bridge that gets put in. A bigger one might make the frame snap.

they may want to replace the stays – depends how thin the metal is and how easily the existing bridges come off.

Replace the stays!! Fairly drastic and not really an option.

They would cut and grind the bridges off rather than apply heat. They will only apply heat with the new bridges.

might be less stiff – I doubt if it would change the strength much.

I’m far from an expert though. 🙂

On-one’s steel frames don’t have bridges, I seem to recall Brant saying that a bridge doesn’t actually do anything but reduce clearance.

I can sort of see his point. In fact I’ve seen a couple of frames over the years that have snapped at the bridge weld.

Perhaps you can grind off the bridge and leave it at that?

Disclamer: Despite being an engineer this isn’t my field and if you die horibly it’s not my fault…..

I’ve been told the same – and my last frame snapped at the bridge due to the stress riser it created – no bridge now.

I am almost completely convinced chain stay bridges are there to hold mudguards on.
Seatstay bridges are pointless on disc braked frames.

don’t they hold mudguards on?

But most steel frames without them seem make a point that they have been engineered with a solution to avoid using them – eg small gussets on the chainstays/bb area. I’m sure mk1 Cotic Souls had these.

Btw – my frame has the disc brake Chainstay/seatstay brace already but still has the other two bridges.

Only real reason I’m slightly worried as it’s a off road steel frame which weighs sub-4lb. So if the bridges are structural I need to ensure that if it’s modded the strength will be the same.

Just get it repsrayed, you’ve coped with having bridges this long. What frame is it? A picture would be an idea?

🙂

My old Inbred (infront of me on the train)has a brace-used for mudguard attachment, though top fixing is drilled/self tapper fixed to seat stay yoke thingy as no bridge.
From memory my other halfs newer model ‘bred has gussets like a Cotic? Idea used originally on the old Bontrager frames to increase strength/save weight.

It’s £110 to get it re-sprayed and only £50 extra to get both the bridges moved. So it seems like an ideal optertunity to make a great frame perfect.

No more for more?