What would be a good build for a 80% city / 20% trail bike?

I recently purchased a Cinelli Mash CXSS frame, I will be mainly riding in the city but wanted to also take it to the trails every couple of months.

I also was thinking of building this up as fixed gear (with a front Canti break), so would welcome points on that too.

First post so take it easy i am new to building bikes but have owned a few roadies before.

  • Complete part selection for a new bike is a very broad topic that has a gazillion auxiliary questions to go along with it, and thus this question is too broad. Commented Jun 23, 2014 at 1:17
  • You may have some success getting a line-up in Bicycles Chat. Commented Jun 23, 2014 at 1:25
  • 2
    I don't think the OP is after part selection rather what type of parts they should be getting, ie road or cx rims, mtb or road drive train, road or cx drops or flat bar, brakes, tires etc...
    – DWGKNZ
    Commented Jun 23, 2014 at 3:23

3 Answers 3


FWIW, Fixed gear off roading is possible if more difficult than needed. This site has lots of useful info.


I ran my Surly Cross Check as a fixed gear scorcher for season or two and it's way to make easy trails hard. It's definitely not for everybody and the downhills can be brutal.

I'd encourage you to go for disk brakes on the front if at all possible and you definitely want a front brake. I also found it very useful to have a back brake as well. Getting any kind of "modulation" in braking with a fixed gear was beyond my skill set, skidding on dirt is a really great way to crash.

Also, an eccentric rear hub will allow you to use a fixed gear wheel with just about any dropouts. White Industries ENO hub has worked well for me.


This isn't really a full answer, and I'm deliberately steering clear of groupsets, but there are a couple of things that are maybe worth considering:

For 80% tarmac/asphalt and 20% trail, maybe you could consider two sets of wheels, if you can afford to do so? (Actually, all you really need is two sets of tyres, but it is far quicker to swap a wheel than a tyre.) It just strikes me that this approach would allow you to run the bike pretty much optimally on both surfaces. But certainly you will find the groupset you decide upon should be suitable for both.

You might want to think twice about brakes, in particular whether you go for rim brakes or disc brakes. Each has pros and cons and they're covered in other questions on this site (for example, note it is quite a contentious topic). But your choice here will probably restrict the groupsets available to you.

As regards running the bike as fixed or single speed, possibly this might help you, possibly not (depends how far along the process you are). But I came across a site a while back called Velosolo. It is a shopping site (and has the various parts required for a conversion), but my main reason for pointing you towards it is because the guy who runs it has also put some decent FAQ articles on the ins and outs of conversions. It might be worth a quick read - in particular the dropouts on your frame will probably determine how easy/hard/cheap/expensive it would be.


I have two CX. One is single speed (not fixed) and one multi.

As for fixie? That is a no on the trail as you lose ground cleareance. With roots, rocks, and drop offs you need to stay on top of the bike. I have single speed mountain bike that I would hate as as fixie.

That is a light racing style frame with carbon fork. Decide if you want to go for weight all the way. You could run an aluminum drive train and race tires like a Cyclocross Speed and have a solid cyclocross bike that does road. Or go with more durability and steel drive train and heavier non-racing tires.

A single speed CX works but the hard part there is gearing it. If you gear it for the top end you don't have enough low end for a steep accent. It is easier gearing a single speed mountain as it does not have the top end. Top end from street is taller than top end trail. Up front use like 36 - 42 chainring. Fairly easy to swap out the rear and the common sizes there are 16, 18, 20. Pick a chainring size that lets you best go from road to trail on the freewheel.

Get CX not road wheelset. Don't cheap the wheelset. On tires you can find some that go both ways nicely like a Continental Travel Contact. Change the pressure from road to trail. They make racers ride in the mud but if this is your city/trail bike then just don't ride it in the mud.

Two wheelsets would be convenient not just for tires but to gear them them differently. But I would put my money in a one nicer wheelset and a White DOS freewheel.

That frame is set up for cantilever so that decides the brakes. I like disc but you don't find many CX set up for disc.

Clipless (as in actually clip like SPD) over a downhill or flat pedal. The reason there is little more torque with the push and pull. It can save you from stalling out on an accent.

I run the bike in the picture below on road and trail. It has 35mm pilot city tires but I ran it on cyclocoss tires for a few years until I got tired of replacing them. I change the pressure by 20 psi as I move from street to trail.

enter image description here

  • Are you hopping curbs on road rims/ tires, had any trouble? Running cx rims and tires allows a lot more flexibility even in the city.
    – DWGKNZ
    Commented Jun 23, 2014 at 3:26
  • @DWGKNZ Those are cx rims and I have not had any problems. Yes I hop. I don't think I have even had a flat on those tires.
    – paparazzo
    Commented Jun 23, 2014 at 13:24
  • @Benedikt Bauer Nice edit. I am not a good writer.
    – paparazzo
    Commented Jun 23, 2014 at 15:35
  • @Blam You have edited this post seven times and I have seen similar activity on other posts by you. Please limit your edits. Each edit of a post bumps it to the top of the list of active questions. Repeatedly editing a post takes attention away from other questions.
    – jimchristie
    Commented Jun 24, 2014 at 18:38
  • @jimirings I added content. Pedals. I did not know that edits had that effect. Will keep edits down.
    – paparazzo
    Commented Jun 24, 2014 at 18:50

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