Peter Treadway

Afternoon all,

New member here, so hope I'm posting this in the right place. Just wondering if I could run my thoughts on a conversion by the experts here, for any holes in my knowledge to be picked apart:

I'm currently in the research stage of converting an old steel framed, 90s MTB in to a drop bar gravel bike. It currently has a Shimano 5 speed freewheel, but I'd like to change this to an 8 speed free hub.

I'm aware of two potential issues with going from 5-8 gears at the back:

1) The pull ratios being different, leading to the current rear mech not indexing properly
2) The spacing between the rear dropouts not being wide enough to accommodate the extra three gears

However, I have a donor bike that I'm taking the 8 speed cassette and wheel from, so am able to use the 8 speed Shimano derailleur from that too. I would then look to use some 8 speed Microshift drop shifters, which use the same pull ratios as Shimano. Would that then work or am I missing anything else?

Also, regards the dropout spacing, I've measured the current spacing as 130mm (which I understand is strange, as old 5 speed spacing is more commonly 120mm but I've tripled checked it and it's definitely 130mm) and the lock nut distance of the 8 speed donor hub is 135mm. As it's a steel frame then, could I cold set the dropouts to accommodate the extra 5mm required?

Any advice on both or either of these points would be greatly appreciated.

Thanks in advance

Peter

Andrew R Stewart 

Peter- I would have no concerns about spreading the rear width to 135mm. Of course care to retain the rear end's being centered WRT the front and keeping the drop outs parallel are important. Most Microshift parts are designed to interchange w/ Shimano, but one needs to make sure before spending $. This spec should be listed in the part's information.

Not asked about is the huge increase of seat to bars reach. Will this greater stretch forwards be comfy and for how long? Also not mentioned are the "new" drop bar levers brake levers being compatible w/ the brakes. Most drop bar brake/shifter levers units are designed around the cable pull for road bike calipers and not a MtB linear brake.

If this is done well a MtB can serve as a great bike, or the bike that reminds one of the mistakes and assumptions poorly made. Andy

alcjphil

If the bike is old enough to have a 5 speed freewheel, it may well have cantilever brakes

Andrew R Stewart 

Quite true. But we just don't know much about this bike yet to do more than lend advise and make assumptions. Andy

RB1-luvr

my 1988 mtb drop bar conversion has v-brakes with Travel Agents. He may want to do that. I'm using Shimano Tourney 3x7 brake/shift levers.

t2p

90’s MTB with 5 speed freewheel ?

130mm dropout spacing ?

most 90’s MTB’s I’ve seen / had had 135mm dropout spacing (and 7 speed and up ... )

t2p

cantilever brakes were still common / fitted on 7 and 8 speed MTBs up through the mid 90’s

mitchmellow62

SheldonBrown.com has a great article on frame spacing and cold setting: https://www.sheldonbrown.com/frame-spacing.html

Peter Treadway

Wow, thanks guys. Didn't expect such quick responses.

Ok, in answer to a few queries:

The bike currently has linear pull/v brakes, not cantilever, although I now gather that this doesn't necessarily help matters. I'll look in to travel agents (that's a new one on me, but I love learning new stuff about old stuff!)

Regards the reach, I had considered this and I've made sure the bike is smaller than my friend (who I'm building it for) would normally ride and am using a riser stem, so I'm hoping that this will address any oversize issues, but time will tell. I'm swapping the quill steerer out for an A head adaptor too, for info.

The dropouts are definitely 130mm though (I've now checked it twice more now since reading t2p's reply ). I had read in a few places that 5 speed dropouts are usually 120mm but happy to be corrected in this regard and happier still that Andy sees no issue in cold setting the frame. I'm looking in to buying either the Park tool FFG-2 for this, or similar cheaper variety, to ensure the rear triangle is uniformly changed.

While I'm listing all the things I'm currently aware that will need to be/I would like to change: It also has a one piece crank that I'm looking to remove and fit with a Truvativ adaptor, so I can fit a more usual BSA square taper BB.

Lastly, for info, should it be a brand known to have strange features, the bike is a Professional Blackjack (I tried to attached a photo but apparently can't until I've made 10 posts here!). I've tried looking up info on the bike but no matter what I google for 'professional bikes/professional bike brand', etc., all I get are results for bikes that professional cyclists ride! . That most I have gathered is that they are now supplied by a company based out of Essex, England... which is where I live strangely! I've sent them an email asking for any info they might have but am yet to hear back.

Thanks again for all the responses though. I really appreciate the advice.

alcjphil

Even later. I had a 1998 GT LTS than had 135mm spacing, 7 speed cassette, and cantilever brakes

Bill Kapaun

Why 8 speed?
9 speed would be as simple and give 1 more gear and more options for cog selection.
They use the same Free hub.
Shifters are about the same price and the 8 speed RDER would work since the pull difference is in the shifter.
You'd just need a 9 speed chain

maddog34

And Cantilever brakes use the same pull ratio as Road Levers/brakes..... so the Thread Starter is on target there.

If the bike has V-brakes, then the road levers will be a mismatch.

maddog34

"Peter- I would have no concerns about spreading the rear width to 135mm. Of course care to retain the rear end's being centered WRT the front and keeping the drop outs parallel are important. Most Microshift parts are designed to interchange w/ Shimano, but one needs to make sure before spending $. This spec should be listed in the part's information.

Not asked about is the huge increase of seat to bars reach. Will this greater stretch forwards be comfy and for how long? Also not mentioned are the "new" drop bar levers brake levers being compatible w/ the brakes. Most drop bar brake/shifter levers units are designed around the cable pull for road bike calipers and not a MtB linear brake.

If this is done well a MtB can serve as a great bike, or the bike that reminds one of the mistakes and assumptions poorly made. Andy"

you made a series of assumptions, andy.

dedhed

Shimano Mt front derailleurs don't often play well with road shifters.

maddog34

From the First post... "However, I have a donor bike that I'm taking the 8 speed cassette and wheel from,"

and, while the 5 speed chain (if it is one) would possibly work, it would tend to be noisy and might also have shifting issues.. like false shifts at inconvenient times.....

Peter Treadway

Just trying to post a quick reply, as the last two long posts I've tried to send aren't showing!

zandoval 

Really? If ya really need 8 or more cogs ta ride comfortably then ya probably need another bike...

Bill Kapaun

Since my lungs are at 28%, LOTS of closely spaced gears are pretty much a necessity for me if I want to ride.
I NEVER tell someone else how many gears they need.

zandoval 

Sorry Bill... What I meant was that there is a point where working over an old style frame to accommodate more gears may not be worth it. Sure... It can be done, but It might be better to go to a lighter more efficient frame set with the needed geometry to accommodate the extra gearing.

Kontact 

Um, a 1990s MTB with a 5 speed freewheel is likely to be Huffy quality with even a sidepull caliper. This is likely not a bike worth screwing around with.

cb400bill

Fixed.

maddog34

Quoted your post to get everyone else caught up on your bike, Peter. And thank you for the additional Info.

grumpus

That was my first thought too - even a six speed was likely to be pretty crap in the nineties.

alcjphil

As well, the one piece crank

Peter Treadway

Apologies again for the lack or replies, guys but I seem to be having real issues with replying!



Anyway, I get some people’s disquiet about the worth of converting such an old frame, but it’s all a bit of fun and I like tinkering around with bikes to see what’s possible. I’m using this frame because it was free, as was the donor bike, so no loss by trying there and even if the new shifters and bits don’t work on this bike, I can keep hold of them to use on another project later.



I’m also making a YouTube video out of it, so even if the project fails it might be useful for others to show what not to do!



I very much appreciate the advice and warnings though. Cheers all.