Mountain bike for road use.....

[Alsajosora]

Hi,
I'm new to these forums so go easy on me please!!!
I have recently returned to cycling after a ten year break. Having decided to lose weight (weighing 18 stone at the time) I decided a mountain bike would carry my portly frame more comfortably over the potholes than a lightweight racer....
I now weigh 12 1/2 stone and want to get more out of my bike.
As I use my bike ONLY on the road I have already put road tyres on it (Schwalbe speed cruisers) but am also going to change the rear cassette (11t-32t) to a road based spread (11t-25t). I also at some point will be dispensing with the "granny ring" (NEVER used it anyhow) and swapping out my middle and outer rings 32/44t atm for a 36/48t combo.(These are the maximums that my BB will allow)
Now I have a Shimano 105 rear mech (RD-1055 model) and am wondering if I could swap it out with the Deore rear mech I have at the moment. The specs say that its max chain wrap is 28T so as far as I can see that side of things should be ok, my question however is will this mech work ok with Deore 9spd rapidfire shifters?
Please, no "just get a roadbike" replies. I have limited funds and the wife would kill me if I suggested I might get another bike.....
Many thanks in advance guys/girls!!!

 

[HovR]

Hi, to the forums!

Hi,
Now I have a Shimano 105 rear mech (RD-1055 model) and am wondering if I could swap it out with the Deore rear mech I have at the moment. The specs say that its max chain wrap is 28T so as far as I can see that side of things should be ok, my question however is will this mech work ok with Deore 9spd rapidfire shifters?

Here's some info I found a while back whilst Googling:

• Shimano mountain bike rear derailleurs are fully interchangeable with road shifters, so select the derailleur based on the size of the cogs. For instance if you want to run a 11x32 cassette on your touring bike you can still use your road shift levers on your drop handlebar, but you would need to swap out the rear derailleur to a mountain bike type to handle that size of rear cog
• Shimano mountain bike front derailleurs are not compatible with road shifters. Road front derailleurs are not compatible with mountain shifters

I also at some point will be dispensing with the "granny ring" (NEVER used it anyhow) and swapping out my middle and outer rings 32/44t atm for a 36/48t combo.(These are the maximums that my BB will allow)

I'd personally advise against removing the granny ring on a mountain bike, there isn't really a practical reason, asides from maybe weight saving - however that difference on a mountain bike will be minuscule (if you really want to make weight savings, replace those suspension forks for rigid ones).

One day you will stumble upon a hill steep enough for you to wish you never removed it. If you still want higher gearing, it is possible to get road and hybrid triple chainsets that are higher geared.

Please, no "just get a roadbike" replies. I have limited funds and the wife would kill me if I suggested I might get another bike.....

Sorry, but I can't resist! The B'Twin Triban 3 is an excellent starter road bike, at an excellent price. I can't tell what your MTB is from the display picture, but selling it may produce a large percentage of the funds needed for a Triban 3. Keep it in mind if you ever find yourself wanting to buy a road bike!

 

[Peteaud]

As i read it you have 9 speed Deore rear mech so by putting on a 9 speed 105 the shifters should still work. The 105 rear with the front rings and rear cassette will be near as damn it a compact so i cant see why it wont all work as it should.

But to my mind you are doing all of this to gain the 48 front from the 44, you still have 11 on the rear anyway. So I cant see the gain is enough for all the faffing about.

 

[Alsajosora]

But to my mind you are doing all of this to gain the 48 front from the 44, you still have 11 on the rear anyway. So I cant see the gain is enough for all the faffing about.

Not true, the rear cassette is biased towards off road riding and as I stated, all my riding is on road. 36x25t will see me up any incline in my area. (Check Vigo hill in the Gravesend area or Boxley hill in the Chatham/Maidstone area )
I used to ride a road bike for years and am comfortable rolling a bigger gear along flat roads, 44x11t on a slight decline is quite easy to spin out.
Soooo, as my riding will be on road I feel a road cassette coupled with a road rear mech (I already have this lying around) and its shorter cage would just be a bit more efficient than ones designed for being jolted everywhichway off road. Also I like faffing.....

 

[Peteaud]

But the rear cassette is changed to a 11-25 you still have an 11 tooth rear, all you have changed is the low end to get closer ratios though the range.

You will have to change the chainset to a 48 to get an advantage.

Change the front and the rear cassette and replace the rear mech to a 105 all in one will work, but you still going to have an issue with the triple front and the chain wrap.

 

[Peteaud]

Sorry, manners

Welcome and well done on the weight loss.

 

[RecordAceFromNew]

Without further info about the state and condition of the existing rig Peteaud's logic seems sound to me, especially in relation to the chainset and rear mech, I guess if I want closer ratios I would consider just changing the cassette. Well done for the impressive weight loss (and undoubtedly fitness improvement) by the way!!

 

[Alsajosora]

My thoughts are that by going from a 11-32t to an 11-25t would give me a more efficient spread. Is this not the case?
Chain wrap, if the max that the rear can take is 28t and I am only going to 25t how is this a problem? (Sorry but as I said I am a bit new to this side of things!! )
Thanks!

 

[Alsajosora]

Without further info about the state and condition of the existing rig Peteaud's logic seems sound to me, especially in relation to the chainset and rear mech, I guess if I want closer ratios I would consider just changing the cassette. Well done for the impressive weight loss (and undoubtedly fitness improvement) by the way!!

What info did you need to know?
Front/rear mechs both Shimano Deore. 22/32/44 Rear cassette 11/32. BB axle length 113.
Proposed changes 22/36/48 11/25 and transplanting the current Deore Long cage rear mech for a short cage 105 road mech.
I know it seems like "faffing" but as I stated already I like to faff!!!! Also as a new bike isn't an option, I want to try and get the best out of my current steed!!!! (Which is only 6months old )

 

[Peteaud]

looking at the specs for 105 the max total cap is 27

You have 26 with 11-25 and a 32/44 front so it will work.

By going to a 36/48 front you would have to alter the chain length, but the 105 will still work

(had to do the maths)

 

[Alsajosora]

Soooooo, it looks like my next weekend off is going to be a busy one.....
Thanks for all your advice guys!!!

 

[Peteaud]

The 22 front cant be used tho, as long as your ok with that enjoy.

Not sure how you are going to stop the front mech changing to the 22T?

Are you going to remove the 22?

 

[Alsajosora]

Had thought about removing it or just adjusting the stop screw to stop the mech going that far over....Not really an issue because I never use it anyway..

 

[Peteaud]

Had thought about removing it or just adjusting the stop screw to stop the mech going that far over....Not really an issue because I never use it anyway..

I would adjust the stop screwto make sure it cant change down to the 22T

Only because if you do change by mistake it could smash the rear mech to bits and/or lock the wheel up.

Either way you could suffer a nasty fall and in traffic the results could be fatal.

Best to be safe than sorry.

 

[Alsajosora]

Sage words indeed sir!!!
Stop screw it is then!!!