Considering a heavily discounted bronson 2 alu frame. Trouble is I’ve just bought a new dropper post in 30.9 variety, and the bronson is 31.6

Domt really want to have to sell a brand new transfer post and replace it so can I shim? Guy’s at jungle seemed to think it was fine, I mailed santa cruz directly but no reply.

Concern stems from the fact the seat post protrudes way beyond the top tube. Anyone know what the min insertion is on a large frame?

My other option under consideration is a bird 145 which Ben has already confirmed is fine to shim. Both frames are roughly same price, but if I need a new post the bronson becomes more expensive.

With a very long shim, yes.

It would have to be long enough to extend past the top tube junction though.

Yeah.. And try as I may I can’t find one longer that ten cm which I think will be pushing it. Unless someone tells me the min insertion on the frame is less than that.

I could try to stick two together but not sure how I’d do that as the lower one would slide off into frame over time

Which dropper? A good shim might cost over ten quid while the outer tube if some droppers can be had for £30.

Fox transfer.. Don’t see an outer tube available after market

The nice folks at santa cruz have just this minute got back to me..

‘Shims are just not as good as using the correct size post, as they do not provide as much support down the full length of the post/seat tube interface, but if you are going to use one, make sure it is at least 100mm insertion.

Your frame warranty would be 100% valid, but if the shim use is the cause of any frame damage, it will not be covered under the “Manufacturing Defect” warranty’

So that’s a no from them then… Although I may risk it with a really long shim ( 15 cm plus) given I can’t see what the difference would be between that and a normal post

Personally I’d wear the cost of replacing the dropper – or buy the Bird 🙂

Buy 2 shims, glue one to the lower portion of the dropper post, it’ll be fine

Yeah..

Why is a relatively budget alu frame like a bird totally acceptable, however I imagine if I bought an alu santa cruz, rather than carbon , which will still be a great bike, it’ll always feel like I’m driving a bottom of the range Audi..

Ironically the carbon version has a 30.9 seat tube. Screw spending 3k on one however.. And it doesn’t appear the cheaper c model is available as frame only

Ask the question about swapping the lower tube on the post. I had it done for a Thomson, you don’t see any spares listed for those ever, anywhere.

My carbon spesh came shimmed with a dropper, the frame is 34.9 and the dropper is 31 something, the shim is only a few inches long too it doesnt cover the entire inserted length and I have had no issues.

I dont think you need it to go the full length of inserted post as the seat clamp applies the pressure for it not to move.

The seat clamp applies pressure to keep the post vertically stable but there’s potential for cantilevering, hence the packing support recommendation.

Whether this is a real world problem or an engineering possibility that will never occur outside of XCO level seatpost abuse is a different matter. I’d probably do it, but really it comes down to rider weight, power output and belief. IMO, if you aren’t going to trust it, the constant worry will spoil the bike for you whether you break the frame or not.

I’d never considered the possibility of getting the inserted section of a dropper upsized. If others are managing it, it’s got to be worth enquiring about.

I wouldn’t have any problem at all.

I have had a shim in probably my last 3 bikes (standard USE one) as I have a 30.9mm post and most frames are 31.6mm now.

In fact on my HT, I’m so cheap, I’ve got an old plastic milk bottle cut and used as a shim.

I’m generally irrationally anti-shim simply because of pre-dropper experience of faf in the hills when raising and lowering posts with shims that want to love the post and not the frame.

Mostly that’s just carried over for me so I’d prefer the right size even though I’m rarely going to move a dropper. They can look a bit fugly though, which could be a consideration, although you won’t see it while you’re riding!

I thought the reverb has a minimum insertion of only 8cm, and 10cm is usual for any seat post. I can’t see why any more than 10cm would be needed for the shim.

If anything happened you wouldn’t leave the shimmed seat post in anyway when going for the warranty, just get a cheap 31.6.

I don’t see what the difference between 10cm of shimmed post to 10cm of post is? As long as it’s min insertion, then it’s the same isn’t it?? I use a shim on my £3k carbon frame.