First off, first time poster long time lurker :-).

There seem to be plenty of happy On One owners here so I thought you could help.

I’m 6’ ½” with a 33” inside leg, 14 stone and 35 yrs old. I mostly ride tight, steep muddy singletrack (Clent/Walton Hills) and occasionally Cannock Chase, I’ve been riding for 6 months & current skill levels are low, but I’m generally good for a go.

I need a frame replacement for my GT Aggressor XC2 (medium 18”) which I have to admit is too small (lower back pain). After loads of looking I have settled on the On One Inbred frames due to their generous TT, low price and favourable rider opinions. BTW I’ve changed the stock fork on the GT for a 100mm Recon Race (Suntour XCR was like a pogo stick))

Like a lot of others between sizes I’m torn between getting the 18” or the 20” Inbred.

Horiz TT length:-
GT is 22.75”.
Inbred is 23.7” & 24.1” for the 18” & 20” respectively

My Current setup is a 120mm stem, 1” layback seat post, 660mm x 20mm riser bars, bars 1” below saddle height. This has pretty much cleared up the back pain problem so I think I’ve generally dialled in the riding position that suits me. The problem now is the long stem compromises the bikes handling and my confidence hence the frame change.

Despite only a 10mm difference, TT length wise the 20” Inbred seems like a better bet with more room to go longer, however where I ride I feel an 18” would be more manoeuvrable and give me the stand over clearance I need as a beginner (I come off a lot!).

Having no experience riding either, would the 20” inbred handle much differently to the 18” on tight singletrack? With low skill levels I thought the smaller, lower frame would be easier to move about and help me develop as a rider.

Based on my current setup I reckon I’d need at a 90mm stem on the 18” and an 80mm on the 20” inbred.

Please give me your input.

18" frame with 90mm stem IMO.

You sound like my identical twin – except I'm older

I'd go for the 20" Inbred (which is the size I own).
But you'll also be fine with the 18"

StirlingCrispin, what stem length do you run, and how does the 20" handle?

I'm the size as you and run an 18" Inbred with 100mm stem and layback post.

This may help.

I'm a smidge taller (and younger, and lighter) than you and have run an 18" frame with 50mm stem on the Summer Season and 80mm stem on standard Inbred. You'll almost definitely need a 400mm seatpost, but you may or may not need a layback post.

Personally I'd keep the fork short travel for the riding you've described (80-100 max) or use a 440mm rigid.

Thanks KINGTUT, I've read the crap out of that page already and I'm well and truly in the overthinking phase of my frame choice :?.

See my concern with the 18" is that if I needed to go with a 90-100mm stem this might ruin the steering aspect of the handling, whereas a 20" frame might feel like a boat since I'm already used to a compact frame

I run a 90mm riser stem with an inline seatpost.

It's been ridden hard for five years now on the technical trails around Stirlng.
On big drops I just lever myself off the back and hang on. It must work as all my big crashes have been on my other bikes!

I also own a 18" Sanderson Life (now there's a bike you should have a good look at!) and wish I'd gone for a 20" frame. That said the 18" fits me – but I've had to work hard to get it that way.

Can you find one to throw a leg over and see?

I ride Clent (was there last night) and one of my riding buddies off here has a 18" Inbred (i think, could possibly be 20" i suppose). I'm sure he'd let you have a sit on to test it out.

We're both Bromsgrove based. I have a 21" Inbred but it's a 29er so no good for you to try.

OK, put it this way;

I'm 6'2", 34" inside legs and long arms, I had an 18" Inbred with a 90mm stem, it felt bloody awful on the climbs, changed it for a 20" inbred which at the time felt too stretched, however due to weight loss and improved flexibility I now ride a 20" Scandal (same geo as an Inbred) and a 100mm negitive rise stem! As I now prefer a more stretched race position.

None of that has probably helped you though.

I'm a touch taller than you but my inside leg is a little shorter. I have an 18" and fit on it quite happily, but I'd also fit on a 20" I reckon. The inbred feels really long compared to other 18" bikes I've ridden.

All the inbreds have short headtubes, so to be comfy I've found I need something like a 10 degree stem and 2 inch risers, or a high rise stem and mid rise bars. Or a big stack of spacers under the stem, but that looks odd and means you need to have forks with a long steerer. Or a 100mm fork to lift the front end a bit.

Same height.
20' 26er had a few including a tinbred – lubberly
18' 26er – just sold one I bought for gf – could ride but felt too small for all day
My advice get a 19.5' 29er
J.

Im 6ft 2" and have a 20" 456 you could try for size if you fancy. Im near to you, drop me an email if interested.

I'm 6ft and have 33 inch inside leg. I went for the 18 in the end due to Brant telling me the 20 would be too big. The 18 is spot on for me and i'm running it with a 17 degree x 100mm stem and layback post.

You could try an 18 and if you don't like it, sell it on ebay and you'll probably onlose lose about £20 on it. They hold their value well.

Tron's advice is good.

Had same dillemma when bought mine, albeit 16" vs 18".
(I'm only 5' 9" though).
Took a while to get over thinking I have too much seat-post showing.
Convinced I should be on an 18" & that the 16" felt too cramped.
After a dozen or so rides now I have to say this lot on here were spot on.
Fits perfectly with 90mm x 10deg stem & 1.5" risers.
So glad I didnt buy the 18".
I reckon the 18" would be spot on for you.
Get a decent quality 400mm post though. (Thomson).

Wow, Alot of responses thanks everyone

So I wittled it down to either a 18" or 20", looks like I need to sit on one.

My preference is a smaller frame but the last thing I want to do is buy 2 frames in a row that are too small for me.

NW Alps Jeyer aka Boz – I've sent you an email, thankyou

MrTall – Thanks for your offer also, Will you be riding Clent this weekend?

PaulGillespie – Does an 18" handle ok with a 100mm stem, and as per Tron's advice I have a 225mm steerer tube on my 100mm fork, I left it long so I can be flexible with my riding position.

6ft2" here, 32 inside leg, I have an 18" original inbred you can try if you want, based Stourbridge way.
I might even part with it… was talked into another FS bike whilst driving to work.

i'm 6'2" – 35" ish inside leg. the 18" works for me with a 70mm stem.

i've ridden a 20" – massive stupid gate it was too.

Won't be riding Clent this weekend. Most of my riding mates have kids so most of the riding is weekday evenings and more at the Wyre than Clent.

The full suss 'summer' bike is out now though so the Inbred won't see much action until the trails get muddy again (so around June……!).

Beware the very short head tube on Inbreds though, if you run a long steerer like you do then it'll look gash with loads of spacers on it. High rise stem and riser bars will help combat that though.

Trent, I'm thinking of trying an 80mm stem just to see what happens but so far the bike's handling with a 100mm stem has not let me down. The more I think about it, if you want a fast and nimble singletrack machine then the 18 is probably best, if you want a stretched out mile muncher for use on wider paths then the 20 might be best. At the end of the day though, you need to swing a leg over one.