MTB on 700c as tourer

[sgw]

My own touring takes in as much off road and bridleway riding as possible. I used to use mtb's but have for the past few years been using a hybrid. There is still a fair bit of road and reletivly solid and flat tracks riding involved so the hybrid's larger wheels have become much apreciated. While it has worked very well I am now considering trying one of my old mtb's and fitting 700c wheels. Partly because my mtb bits are of far better quality than my hybrid but also because I think it will do a better job off road. The technical difficulties like lack of brake position and pannier mounts (any others?) can easily be overcome but I wondered if anyone here has already used similar and what their opinion might be.

 

[MacB]

As long as you have the required clearances then it should be great, I did one as a trial but clearances were too tight and couldn't get more than a 25mm tyre on. I've read reports of the handling being adversely impacted but didn't find that for myself. I don't do any offroading of note so don't really need one but have been very taken with the 29er MTB's like the Surly Karate Monkey. I came close to getting a frame to build up as a general/commuting bike. I suppose I've done the same with the Pompetamine frame I'm building up now but that's limited for tyre clearance, maybe 42mm max without guards. Whereas with the KM you could go up to about 60mm tyres.

 

[Crankarm]

I think you'll find that for 700C rims on road hubs, the axles will need spacer nuts to gain extra 5 mm as they will not be wide enough in the 135mm width drop outs of your MTB frame. You could bend the rear traingle of frame inwards to close the gap but I wouldn't advise this as it will stress the rear traingle of the frame and possibly weaken it, but others might not see a problem. If you don't already have 700c wheels then I would suggest going for say Mavic 719 700C rims on MTB hubs because MTB hubs have a wider axle width of 135mm (OLN) which will fit your MTB frame drop outs. However once these wheels are in you might well find that there is much less space between the tyre and the small cross bar that links the rear seat stays this cross bar will need to be moved slightly up and the bosses to mount any V brakes. Maybe your MTB frame does not have individual seat stays going right up to the seat post but a tube with forks much like front forks in which case you will be stuck. Maybe SJS do some modified brakes for this exact application? You might not be able to fit a rear mudguard either due to lack of space. Then there are the clearance issues with the front fork.

I would keep 26" wheels on your MTB, maybe fit a decent hand built pair if you want to splash the cash, fit a decent pair of tyres and see how the bike is then. If you still want to make mods then I would look at your bike's gearing as you should be able to nip along on 26" wheels just as quickly as on 700C wheels and also have the low down gearing for off road and reassurance of the added strength and durability if the conditions are really tough. Although good hand built 700C wheels are pretty strong as well.

HTH.

 

[billflat12]

My own touring takes in as much off road and bridleway riding as possible. I used to use mtb's but have for the past few years been using a hybrid. There is still a fair bit of road and reletivly solid and flat tracks riding involved so the hybrid's larger wheels have become much apreciated. While it has worked very well I am now considering trying one of my old mtb's and fitting 700c wheels. Partly because my mtb bits are of far better quality than my hybrid but also because I think it will do a better job off road. The technical difficulties like lack of brake position and pannier mounts (any others?) can easily be overcome but I wondered if anyone here has already used similar and what their opinion might be.

Have had similar ideas myself ( would help cut down my bike collection ) Frame angles are different for an mtb.

eg. downhill/freeride bikes are stable/robust have slack frame angles & longer wheelbase ( incl. lots of suspension ) but don,t really climb very well either .
A cyclocross type build may be more suited , very similar to your hybrid really, maybe a short stem to improve off road handling coupled with double wall 36 spoke rims & mtb hubs would be the way to go.
I have demo,d a kona 29r mtb with rigid forks and was really impressed with the rolling speed round a blue mtb route. If your serious about going down that route i would recommend trying a 29r first then make comparisons with your intended donor frame on a manufacturer,s website.( remember to check Chainstay lengths for panniers)

see: (The bike i borrowed) http://konaworld.com...fm?content=unit

 

[RedBike]

I had 700c wheels on a standard 26" wheels MTB for ages then upgraded to a 29er.

700c wheels fitted with 23mm tyres are approximately the same size as wide 26" tyres. The problem is, when you start fitting wider 28/30mm touring or cx tyres to a 700c wheel the wheel becomes quite a lot bigger, which means you might get clearance issues.
My 26" wheeled bike didn't really accept anything larger than a 23/25mm tyre.

'Hybrid' / 29er wheels, in other words, rear wheels with a 135mm hub are easy to come by. So getting a set of 700c wheels to fit a MTB isn't really a problem.

(Getting rim brakes to line up however, is a complete nightmare!).

 

[RedBike]

Look carefully at the wheels on this bike, they're 700c on a 26" wheeled bike.

More pics here
http://redbikes.blog...aker-100km.html

 

[sgw]

Thanks

I am not too concerned about tyre width. In fact I will most defiantly err toward road profiles. One of the things I noticed when I went to the hybrid was that for my style of riding the advantages of roadish tyres far outweighed the loss of the advantage of wider or knobblier ones. If I am slogging up a boulder strewn, dried up stream bed with full camping kit, I am likely to be pushing anyway. The times I miss the knobblies is in deep mud, which can soon stop even the most aggressive tyre or damp grassy slopes. Both of which I do find a lot of but by avoiding the first and lowering tyre pressures for the second I can cope with.

I would like to use my old mtb Machine Tech hubs which are cnc'ed from solid and the size of a pop can. Disadvantage is that the freewheel is so loud that should I stop peddling they will flush all wildlife as I approach. Good for clearing towpaths of peds though. Initially due to the cost of a custom build, I might have to settle for a strong set of second hand road wheels. I am quite confident that the rear triangle of the frame, a Zaskar LE, is capable of coping with the required flex. I suspect it used to move by the required 5mm every time I used my old Maguras in anger. I don't know of a stronger frame. I would use my old Maguras or cantis on an adaptor plate.

I am a bit confused about gearing though. I need new rings and cassette so will need to reach a decision on these. I have options of an XTR short cage rear mech which I would prefer to use. I was happy with the gear spread it covered with 16" wheels for primarily off road use and like the crisper changes of a short cage. I am not sure though that it will be as effective with 700's for the amount of good surface riding I expect. I do have the option of a long cage SRAM which will widen the available range and might be the way to go.

Any idea on the effect on gearing of changing from 16" to 700c? I know there are tables but they give me a headache. Just an idea of the %age change would do.

As you say CA, well built 700's are surprisingly strong. It should be remembered that the whole development of 16" wheels for mtb's was primarily driven by tyre availability in the States in the 70's rather than any intrinsic strength.

 

[sgw]

Look carefully at the wheels on this bike, they're 700c on a 26" wheeled bike.

More pics here
http://redbikes.blog...aker-100km.html

Nice bike and nice site Redbike. I will be back when I have time to have a proper read.

Will I find much on your builds or how you arrive at them? Your type of riding, though obviously more demanding and competitive is rather similar to mine. If it works for you it will be well within its capacity for me.

I don't want to reinvent the wheel.

 

[andym]

For larger size frames using 700 or 29er wheels means frame designers have to mske fewer compromises (and the converse applies for smaller frame sizes).

Beyond that it's a bit of six of one and half a dozen of the other - supppsedlu some advantages rolling over stones but at the cost of a heavier and weaker wheel.

Unless you've got really stong reasons for wanting yo experiment - or a spare pair of 700c wheels and no 26-inch wheels - I'd leave well alone.

 

[RedBike]

I bought the 700c wheels very cheaply to play around with turning my mtb into a cyclo-x bike/ a disc braked winter roadie. Unfortunatly the large cyclox tyre wouldn't fit my frame and my cheap wheels were naff so they made the bike very sluggish

The larger wheels mean the gearing is higher. However because the 700c wheels with narrow tyres roll quicker than 26" knobblies the gearing actually 'feels' lower. Even though the gearings higher to begin with you will be able to climb using a higher gear.

 

[sgw]

After considering all the proffered advice, my pile of parts and my finances, I have decided to postpone my 700c mtb experiment. They will fit ok but to get a pair of sufficient quality is out of the question at the moment. I will build it as a 16" mtb with puncture resist road tyres and aim at improving non mtb type performance through gearing selection.

Thanks for all the food for thought.

andym hot the nail on the head with:-

Unless you've got really stong reasons for wanting yo experiment - or a spare pair of 700c wheels and no 26-inch wheels - I'd leave well alone.

 

[sgw]

The rear mech I am using is marked as Max 28 Total - 28.

I am considering 46, 34, 24 & 12/28 does anyone have any thought on suitability of this gearing for gentle but well loaded touring with road, track, and mountains (where I know I would struggle with anything). Bear in mind the limitations of the short mech.

I found a pic of what I am getting at. I know it doesn't look pretty in mudguards but the rear will be covered by rack and pannier anyway. It's almost sacrilege to what must be among the best rigid mtb frames ever. But I want to use it and my serious mtbing days are sadly over.

Any suggestions on the best range I can get with Max - 28 Total - 28 rear. and would it be usable as described above? Failing that, does anyone have a 7/8 spd long cage XT mech for sale?



<edit>
(Strike out my selection above. That gearing is impossible with my mech apparently.)

 

[RedBike]

The rear mech I am using is marked as Max 28 Total - 28.

I am considering 46, 34, 24 & 12/28 does anyone have any thought on suitability of this gearing for gentle but well loaded touring with road, track, and mountains (where I know I would struggle with anything). Bear in mind the limitations of the short mech.

I found a pic of what I am getting at. I know it doesn't look pretty in mudguards but the rear will be covered by rack and pannier anyway. It's almost sacrilege to what must be among the best rigid mtb frames ever. But I want to use it and my serious mtbing days are sadly over.

Any suggestions on the best range I can get with Max - 28 Total - 28 rear. and would it be usable as described above? Failing that, does anyone have a 7/8 spd long cage XT mech for sale?



<edit>
(Strike out my selection above. That gearing is impossible with my mech apparently.)

I was VERY tempted to set my 29er MTB up just like that. (Mud-guards + drop bars). The ony thing that stopped me was the price of STI shifters and the cost of Avids road disc brakes. Also getting a rear (or front) pannier rack on was a major pain.

Have a look at this thread. These are the sort of bike I think you want? (Well I do!)
http://forums.mtbr.com/showthread.php?t=355649&page=1

As for the gearing. I would just stick with a standard MTB chainset. 22,32,42. (Will this work with a short cage?).
Once the bikes loaded up you wont be able to pedal out 42x12 without the aid of a BIG hill, and you might apprechiate that 22t granny ring on some of the steeper climbs after a long day in the saddle.

 

[sgw]

Another great site RB thanks. I would like drops but am a bit worried about a lack of leverage when off road and loaded. Anyway, I can't think of bars and levers till I get these gears sorted.


This quick throw together of bits is still troubling me. Any help on selecting a workable range with this mech would be gratefully received.

The mech is marked:-

Max 28t
Total 28t

My original idea (28-12) + (46-24) = 38t.



With your suggestion of:- 22,32,42 and 12-28 cassette thats:-

(28-12) + (42-22) = 36

Other options are:-

(26-12) + (42-22) = 34

(25-12) + (42-22) = 33

(26-13) + (42-22) = 33

None of which would work with my 28max cage! I will have to look out the old cassette and count. It ran with 46/36/26 rings but thats still gives the same -20 for the sum.

Am I doing that right? Gearing drives me mad! I want a Rohlhoff

Any suggestions?

 

[RedBike]

I mistook the 28t max to mean that the largest sprocket your rear mech could handle was a 28t, instead you mean it's capacity is only 28t ?

Most modern short cage road rear mechs are 28-30, and these are designed for a double chainset and a racing (close ratio) road cassette.
You'll always struggle to get a short cage mech to work with a triple of any size.

It sounds like its new rear mech time!


*You can fudge things and exceed the capacity of the rear mech by several teeth if you're willing to accept that the chain will be too slack to allow you to use the smaller sprockets on the cassette while in the granny ring. This is a fudge though, and not really recommended.