putting 26 inch parts on a 27.5 frame

Hi ,

I have an old 2005 Full Squish meta that I always felt was too small for me and positioned me dangerously forward. I am eager to own something with the newer geometry.

I am eyeing up a 27.5 Brand X hardtail frame that I see will fit me much better and has the long toptube thing going. I am considering just swapping over the parts and selling the meta frame with its shock to offset the cost a wee bit.

So Id be putting 26 inch wheels and a 140mm travel 26 inch fork on a bike that recommends 130 mm travel and 27.5 inch wheels using a headset adapter to keep the straight steerer.

CRC say they cant recommend it as it is a frame built for 27.5 wheels but in the Questions section for the frame I see people are running all kinds of wheel sizes and fork travels with that frame.

https://www.chainreactioncycles.com/ie/en/brand-x-ht-01-27-5-hardtail-frame-2019/rp-prod130452

As you can tell funds are tight. If I can pull this off Id have a newer geom bike that I could upgrade to 27.5 down the line or will I have a deathtrap with badly compromised geometry? Any thoughts appreciated

J

Friend of mine put 26″ wheels on a 275 frame and forks. First ride out he fell off and broke his finger ‘cos he was going too fast.

Take from that what you will.

If it were me, I’d go ahead and try. That frame is intended for a 120 mm fork, so the 140 mm will lift the bottom bracket back up to partially compensate for the smaller wheels. The head angle and seat angle will be a bit slacker, but I’ve never actually found that to be a problem. I’d run the biggest tyres I could fit to try and lift the bottom bracket up a bit more.

You’ll cause the heat death of the universe.
Or it’ll be fine, barely noticeable except for a slightly higher risk of pedal strikes.

won’t make any real difference. I’ve got 26 inch wheels and a longer 26 inch fork on a transition scout.

I have done this with the BX frame as a second/backup bike. I put a 150mm x fusion slant 26er fork and 26” Stan’s flow wheels. Loving it but it is very low. Have had to adjust my riding style to suit. With a 140mm fork it might be too low??
I also put 170mm cranks to reduce clipping the pedals. It made a small difference.
I also drilled the frame for a BX stealth dropper :-).

26″ in a mk1 Switchback here and it works brilliantly*. I’ve had the same wheels in a BFe, Flare, Rocket and Stereo 140 (all 650B). It’s only 12mm difference in the radius of the wheels, you won’t die and there’s usually loads more mud clearance for your lighter, stronger wheels 😀 No need to ‘upgrade’ to 650B, mainly because it’s not a **** upgrade, it’s just a different size wheel.

no death-

again, no death-

* so much that I’d bet 10p that it was meant to be a 26″ frame originally…

The wife has a 26in wheels in an On-One 45650B.

She doesn’t seems to have suffered any firey death type consequences but i did built it up with 170mm cranks and thin pedals.

Just built up one of these with 27.5″ Planet X El-Guappo/WTB wheels (don’t forget the 135 QR end caps), rigid forks (49cm A2C), 1×9 drive train, SLX brakes. Very nice ride, loving it for playing around on during commutes home.

Will be a bit lower with 26”, fit shorter cranks. Tbh, I’d be more concerned going over spec with the fork although 10mm is unlikely to lead to torn off head tube time. 10mm will roughly slacken the HA around half a degree. Depending on axle-crown numbers, you may or may not mitigate the BB height with the bigger fork. So long as the quoted BB height with 27.5” isn’t under around 300mm you should be fine I’d think with shorter cranks.

Thanks ,

So if you have a 140mm fork on a bike that takes a 130 BUT you run 26 inch wheels instead of 27.5 will the smaller wheel cancel out the extra fork travel ?

Is a 27.5 frame with 26 inch wheels just like a 27.5 bike with the tyres deflated a lot is what I think I am asking ?

Ive had 26 bits on a 275 for a while now, the main problem is that the bike keeps exploading in the most inconvenient places although since I have put 27.5 forks on the bike only catches fire. It was a problem the first few times, but when you learn the warning signs such as sparking around the head tube it’s easy to prevent by emptying you hydration pack on the frame. Given this information do you really want to put a 140 fork on a 130 frame?!

Really though, I dont think the wheels make much difference, changing the fork has, the bike feels slower to respond with a 275 fork on.
The extra length of fork might make the bike a wander a bit on climbs. With heavy use could it damage the frame?

If you can lower the fork I would say go for it, and don’t worry the bike will be fine, maybe a few more pedal strikes as suggested above.

Those 27.5 planet x wheels are out of stock but on sale for £90 right now.
https://www.planetx.co.uk/i/q/WBI25EGRS/wtb-st-i25-tcs-rim-on-el-guapo-rattlesnake-hubs
If get them to email when in stock and you’re lucky you might get them for that price maybe? Or wait long enough they’ll be on sale again a few weeks later.

I’d be more concerned going over spec with the fork although 10mm is unlikely to lead to torn off head tube time

A longer fork will not tear off your head tube. A 120 mm fork is generally around 500 mm axle to crown. If you add 40 mm to that, you’re changing the length by 8%, so the bending loads on the headtube will increase by 8%. That’s not going to cause the headtube to just fall off. What will make a difference is if you take a lightweight XC frame, put a big fork on it, then go jumping off silly stuff and blasting through rock gardens at warp speed. If you ride sensibly, a 30 mm increase will not cause any problems.

How much clearance have you got for honking big tyres? 26+?

So if you have a 140mm fork on a bike that takes a 130 BUT you run 26 inch wheels instead of 27.5 will the smaller wheel cancel out the extra fork travel

no. 26 inch wheels will only make it lower, change the WB and trail. you can run a longer 26 fork so say a 150mm 26 pike rather than a 140 27.5 pike.

How much clearance have you got for honking big tyres? 26+?

2.4″ max iirc.

****, that black bike’s nice. Braaaaaaaaaaaaaaaaaaaaap! What is it?

I built my son a brand X ht01 with 26 last summer.

Works fine. I put a 145mm 26 fork on it, which I calculated didn’t make much of a change of the 120 27.5 fork, given the shorter travel but longer stanchions.

It does have 155mm cranks on it though, but that’s because he’s ickle.

I’ve built a Dartmoor primal up with 26″ wheels, wasn’t an issue. Currently on an NS Eccentric with 26″ hoops,rides better than when it was 650b. Go for it is all I can say.

I sometimes run 26″ wheels on my Bird Zero AM, with mud tyres to improve clearance.

Can’t say I’ve noticed some big difference.

You’ll be just fine, with both wheels and fork length too.

sod all difference between 26in and 650b when you look at the rim sizes, I reckon it will be fine. Whats the worst that can happen??

What’s the worst that can happen? We’ve been through this already on this thread, in order of awfulness-

1. Heat death of the universe
2. Fiery death
3. Exploding bike
4. oh, nothing, it’s fine and I was worrying for no reason.

Currently have my new shape BFe setup with a 650b back wheel, old 26 inch Fox 36 forks and a 26 wheel with a dirty massive maxxis shorty. It looks a little odd up close but rides great. Initially setup totally 26 and was also fine.
Admittedly as soon as I can afford some 650 forks I will swap out.

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I’ve got one of those frames, built it up last year with a 140mm fork. It rides well, BB isn’t too low so might take 26 wheels without too much of a problem.

There’s not tons of clearance for chunky tyres, 2.3 is tight on 27.5 but you might get away with something wider on the smaller wheel

Not sure if that will work? In theory its a picture of a BFe 650 with 26 inch wheels….

BFe
Ok maybe this

Thanks for the advice folks , operation was a success , very happy with how the bike rides.

IMG_20190216_121611 by

glad you like it. Looks good. Those brand x frames look brilliant value.