Cyclocross and Gravelbiking (Recreational) This has to be the most physically intense sport ever invented. It's high speed bicycle racing on a short off road course or riding the off pavement rides on gravel like :The Dirty Kanza". We also have a dedicated Racing forum for the Cyclocross Hard Core Racers.

Gravel bike conversion?

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Old 01-11-19, 07:50 PM
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BrazAd
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Gravel bike conversion?

I have a '84 Trek 400 that is all original. I got to looking at it in the garage tonight and it occured to me... it's got tons of room for wide tires... the width of the rear wheel dropouts is about the same as my '15 Cannondale Synapse 11-speed. There is already small clamps on the top of the top tube for a cable that is running back.

Would this frame make a decent candidate to convert it to a gravel bike? Thoughts? Opinions? Experiences??

Thanks in advance,

Gary
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Old 01-11-19, 08:00 PM
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tyrion
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Caliper brakes will limit tire size.
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Old 01-12-19, 10:28 AM
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Originally Posted by BrazAd View Post
I have a '84 Trek 400 that is all original. I got to looking at it in the garage tonight and it occured to me... it's got tons of room for wide tires... the width of the rear wheel dropouts is about the same as my '15 Cannondale Synapse 11-speed. There is already small clamps on the top of the top tube for a cable that is running back.

Would this frame make a decent candidate to convert it to a gravel bike? Thoughts? Opinions? Experiences??

Thanks in advance,

Gary
the width of the rear dropout doesnt play into if a frame can handle wide tires.
your Synapse is going to have a 130mm dropout which is the current road caliper size. Tire clearance will be limited by the chainstays, specifically closer to the bottom bracket. Also the brake bridge will limit tire size.

as for your trek, that will have 126mm spacing in back. It may be able to handle a 35mm tire and at worst it will handle a 32mm tire once converted to 700c.
good news is that its a 27" wheelset stock, so swapping those for a 700c wheelset will give you that bit more tire clearance.

as for the clamps on the top tube...those are cable guides for the rear brake. Those dont have anything to do with if it would be a good conversion and have everything to do with if you simply want to stop while riding.

it would be a pretty limited use gravel bike for me based on style and tire clearance, but perhaps somewhere with hardpack dirt roads could be a great place.

if you want a gravel bike on the cheap, but an early 90s hybrid. Tons of clearance, typically relaxed geometry, and wide range gearing by way of a 3x7 drivetrain.
toss some new bars, brake levers, and shifters on then ride.
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Old 01-12-19, 11:18 AM
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There are people who like to put 650b tires on these older steel road bikes. But, the conversions may require adding cantilever brakes. I.E. Some brazing.

I second the opinion on Hybrid to "Gravel" conversions. They are rugged bikes for a base.
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Old 01-12-19, 09:28 PM
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Let me clarify some... not sure I did a good job explaining my question.

Would the *frame* for the '84 Trek 400 be a good candidate to fit it with all new parts - brakes, wheels, groupset, cassette, etc. - to make it a gravel bike? Heck, even the handlebars are narrow and older and need upgrading, along with the seat post. The *only* thing I'd keep if this might work would be the frame!

Reading the above responses (thanks for those, by the way!), I'm thinking I'd be better off to buy a used gravel bike that is ready to go.

The Trek 400 is a good frame, that's why I thought it might be cool to "repurpose" it.

Thanks for the input - keep it coming!

Gary
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Old 01-14-19, 10:47 AM
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Biggest problem I have with a bike like that is down tube shifters don't play well with knobby tires. I've missed a shift and torn up my hands! ;-)

That bike looks like it has a short wheelbase and a steep head tube. Not great for gravel. I wouldn't put any money into it for gravel.

I also find that the rear tire tends to be close to the seat tube and that the chain stays tend to be pretty narrow - making anything bigger than 32mm hard to fit. A 32mm probably won't fit under the brake bridge. Nice frame, but not designed for gravel, and not worth the $$$ to modify, IMHO.
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Old 01-14-19, 07:32 PM
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The Trek 400 is a nice frame and might make a fine conversion. The thing to check before proceeding is tire clearance. Will it accommodate the size tires you want to use? In my experience older steel frames with the sort of sport-touring geometry of your Trek make fine gravel bikes if the tire clearance is sufficient.

Here's a couple photos of conversions I've done. The first one is an early seventies Motobecane Le Champion. The second is an eighties Diamondback Hybrid.






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Old 01-14-19, 07:40 PM
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Someone else already converted one from 27" to 700c, looks like it went pretty well:

https://grassrootsmotorsports.com/fo...e/29370/page1/

Dang, that's some generous wheel clearance you've got on that bike. I'd go for it myself, without a bit of hesitation.


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Old 01-15-19, 09:44 AM
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I've done a 700c conversion on an early trek and it fit 35s. If your gravel roads are fairly tame then it would make a fine gravel bike.
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Old 01-16-19, 10:47 AM
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Originally Posted by BrazAd View Post
The Trek 400 is a good frame, that's why I thought it might be cool to "repurpose" it.

Thanks for the input - keep it coming!

Gary
Being a 1984, was this originally a frame made for 27x1 1/4" tires? If so, you can probably fit 700x35-37 tires in there due to the slightly smaller diameter rim of the 700c setup. Your limiting factor will likely be the chainstays. Also, find as wide a 700c rim as you can. The wider rim will plump up the tire and keep the rummer from flopping around with those wide tires for one, but also keep the braking surfaces further outboard, which helps with clearance for brake calipers. If your rim is super narrow (classic road rims) then the wide tire will end up in a "lightbulb" shape that may hit the caliper arms, as well as not being so stable for cornering. An internal rim width in the low 20's would be ideal, but those are getting hard to find for rim brakes it seems.

If you've got DT shifter brazeons on the frame and have brifters in your parts stash (or are willing to buy some old shifters from eBay) then you can get cable ends from several sources that will bolt on where the DT levers used to go. I've done this on four bikes and it works great. Modern or classic brifters and drivetrain and a classic frame play just fine together. I suppose the old stem shifters already come with a DT cable stop, so that would work fine as well.

Naturally, this all depends on what you call "gravel". If you are talking about riding dirt and gravel roads traveled by cars, you'll be fine. If you are thinking of using the bike as a rigid, drop bar MTB on gnarly singletrack then you will likely be disappointed.
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Old 01-17-19, 02:11 PM
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Originally Posted by shoota View Post
I've done a 700c conversion on an early trek and it fit 35s. If your gravel roads are fairly tame then it would make a fine gravel bike.
Ditto. I converted my 86 Ross Centaur to 700c and fitted specialized 700 x 34 cyclocross tires with no problem. Probably wouldn't do well in mud due to minimal tire/brake clearance, but I rode hundreds and hundreds of miles on dirt roads all over southern Georgia.
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Old 01-17-19, 03:24 PM
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Originally Posted by chas58 View Post
Biggest problem I have with a bike like that is down tube shifters don't play well with knobby tires. I've missed a shift and torn up my hands! ;-)
I don't think I've ever missed a shift and hit the tires.

Since just about every bike I ride has different shifters, the biggest issue is remembering where I put the dang shifters on the bike I'm riding.

There are cable stops for DT shifter posts. Not a big deal if one wishes.
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