so old MTB frame to gravel bikes? thoughts? update on 30/06/24

[jonnyboy666]

ok so like many of you i have a fleet of bikes, i love having my retro stuff but to be honest i don't ride them much, i keep a few at the shop as talking points and that will expand with what i'm doing in the shop over the next couple of months. but anyway i started seeing stuff on instagram etc and youtube where people have got older MTB frames and converted them for gravel use, i find this a little interesting as i have not been particularly enamoured with any of the recent gravel bikes i have built for myself, the Kona Sutra was nice but i was recommended the wrong size from the rep, so i sold it, then got a Kona Rove, built it with GRX, it road fine but a little harsh at the front with an alloy fork, so i put it back to standard and sold it, i then put the GRX group on a Rocky Mountain Solo, it's nice enough but a little dull and then i started seeing the videos.

example:-

so here i am looking at my Rocky thinking about what frame could i get to convert to a gravel bike instead. now as i have loads of bikes i realised i don't have to buy anything because i already have something! yes! my unused in years but mint 2007 Orange Clockwork, it's 26" wheel, quick release, it's got a rigid carbon fork in it, it's disc only.

it just seems to be it'll do the job, i couldn't find the exact geometry on line but i did find the geometry of another orange frame, the 2009 Evo8, and compared it to the modern RX9, both in a medium size

RX9 head angle is 70 degree, the evo8 is 71
RX9 seat angle is 74 degree, the Evo8 is 73
RX9 top tube is 527mm with a 90mm stem =617, the Evo8 is 566mm and i think has a 100mm stem =666

now i always found the top tube of my clockwork a little short so i ran i think ayt one point a 110 stem, so i'm thinking that if i run a gravel bar in it i could use maybe a 50mm stem and the bar position should be about right.

having looked at a few videos, the 26" bikes can fit 700c wheels if the tyres aren't too wide and therefore tall, but should fit 650x45 without too much trouble. i'll have to run an mtb chainset and front mech but it already has that but i might need to change the ring sizes.

so have any of you motley crew done it? do threy ride ok? any pitfalls?

 

[Frankenorange]

I have done it with a '98 Orange O2 frame, as a base. Still on 26" wheels and canti brakes and there have only been two problem areas with the build. The first has been the lack of choice when it comes to 26" tyres if you want 45-50mm and a tread that is suited more for routes with lots of road miles with gravel links.
The second was finding an off-the-shelf lightweight rigid fork, for 26" wheels, that had the right A2C and rake combo. Getting this right has changed things from very good to bloody amazing!
I started with nothing but the frame so i had all the usual time and money consumers when it comes to fit and drivetrain experiments, but if it had been a complete bike to start with, or if i had a bunch of bits that i knew for sure worked on the frame, it would have been a doddle. I have tried a whole bunch of different gearing setups and i am now trying 1x as i really was carrying around a load of gears that i wasn't using.
Fit wise i went for what i would have on a road bike. My off-road bits are pretty much what you will come across on The Forest. Disused railways, hardpack, fireroads, gravel on tarmac/concrete etc so closer to road riding than singletrack and jumping about.

I say do it. Mine feels like a road bike, with some more squish in the tyres, and it whips along just fine and off-road it feels like a CX bike, with more squish in the tyres so ticks all the boxes.
I think the only advice i would give is to not use a retro frame that ends up needing a really short stem and has really slack angles. Front end should either be a rigid or had max 80-100mm travel fork. Idealy aim for a frame that you can transpose your road frame onto(or as close to as poss) and remember you can steepen the angles with a lower A2C fork. The higher built in BB height is your friend with these frames.

 

[hamster]

A pal has done exactly the same conversion on an early 2000s Orange P7 - it seems a pretty happy conversion so I think you are starting from the right point.

 

[Frankenorange]

Forgot to say i use regular width road bars. Well narrower than what might be normal as that is what works for me.

 

[novocaine]

stop thinking, start doing.
2008 (I think) GT avalanche converted with 700c wheels (can take 26" happy enough with 2.1 tyres).

https://www.retrobike.co.uk/threads/g-t-average-lance-2008ish-gravel-🤢-bike.464307/

 

[JCS]

This Rockhopper is really well executed

 

[bikeworkshop]

We'd always suggest getting a disc- specific fork if you want to run a front disc - there's a significant point load at the top of the caliper that the old tubes definitely weren't designed for.
You can build in reinforcement, but there are still forces it wasn't designed for at the dropout and the crown. The best fork is the right one.

It is hard finding a nice steel disc fork in many lengths - we offer surly, salsa, soma, things like that.
They are a lot heavier than the highest quality of the 90s, but for good reason. Your life depends on it.

90s mtbs have very similar geometry to touring or Gravel bikes so it's just a case of getting the parts.
Go for it

 

[jonnyboy666]

ok, so as it's my day off i decided to go to the shop and start messing about, got the tape measure out against my rocky mountain solo and my old clockwork, reach wise once the correct stem is fitted i think it'll be fine that way. obvs the frame is disc specific and it has a rigid carbon disc specific fork, so i pulled a pair of hybrid wheels out of a customers bike which have 700x35 marathon tyres on a test fit, see pictures, i was thinking 38mm tyres so here's the clearance i have.


fork, no problem at all



rear end i think a 38 might be tight, but i think i'm gonna try it, it's the height of the tyre more than the width that is a potential issue.


chainstay is no issue though




gear wise this bike has a double 28/38 ring set up, i think that because of having to use an MTB chainset and front mech i think i'll leave that on, see if it works with the GRX gear lever, hopefully it will, i haven't checked compatibility. i have some Deore calipers that are post mount as the GRX flat mount won't fit with out looking terrible with strange mountinmg brackets, i have an FSA bar/stem etc. this bike has Hope hubs so i could just rebuild them in to some 700c rims but i think i'll just sell them and build some XT hubs i have in to some mavic rims i have.

should be an interesting project.

 

[bikeworkshop]

I think with a double up front, the slight differences in shimano cable pull can be overcome.
38 largest up front might be a little small if you've got Drop bars and 700s on tarmac (and don't want to do sram xd) but you can just stop pedaling!
GRX is much better with mountain than road as a rule, and up front it really wants a wide chain line like mtb

Give it a go!
Plan a ride!

 

[novocaine]

that up there is a 34x11-28, on road it settles out around 16-18mph but can be spun to more, I could go taller on the front and still be comfortable but wanted the lower end too.

looks like you have a full plan there Jonnyboy, you might find the exotic fork is a bit toooooo wide and looks odd, or you might not care at all.