Upgrade old MTB from 18 gears to 21?

[fasturtle]

Hi everyone.
I have an old MTB. I want to upgrade the gears from 18 to 21. Could I just get a new wheel that has the 7 speed cassette on it and fit it to the bike. The derailers seam to have the range for it. I know that I will have to buy new shifters for the extra gears.
I did a search online and couldn't find anything.
What would I actually have to do?
Any ideas?
Thanks.

 

[Ajax Bay]

Yes will probably work.
Note that you don't have a cassette, you have a freewheel and block (6 sp). A 7sp block would screw on there and may be easier than getting a new wheel. Your LBS will likely do this quickly and easily. Doing it yourself is theoretically easy, as is the 'process', but practically hard (freewheel tool, big spanner, length of pipe, a way of making sure the frame/bike doesn't move).
Highly likely that an old MTB has an over lock nut distance of 130mm but if you procure a new wheel it'd be worth just checking. MTB wheels of the kind you're likely to go for may be 135. Note also that you have rim brakes.

 

[fasturtle]

Yes will probably work.
Note that you don't have a cassette, you have a freewheel and block (6 sp). A 7sp block would screw on there and may be easier than getting a new wheel. Your LBS will likely do this quickly and easily. Doing it yourself is theoretically easy, as is the 'process', but practically hard (freewheel tool, big spanner, length of pipe, a way of making sure the frame/bike doesn't move).
Highly likely that an old MTB has an over lock nut distance of 130mm but if you procure a new wheel it'd be worth just checking. MTB wheels of the kind you're likely to go for may be 135. Note also that you have rim brakes.

Thanks.

 

[Reynard]

If you want to have a look at how it's done, then check out this thread: https://www.cyclechat.net/threads/secondhand-raleigh-junior-rigid-mtb-lemon-or-worth-a-punt.264186/

I took a 15 speed steel MTB up to 24 speed. It did involve a new wheelset as I went from a freewheel to a freehub, and I did need to cold-set the rear triangle to accommodate the new rear wheel, but if done with care and good planning, it's definitely do-able.

 

[All uphill]

If the budget allows its nice to go to freehub, especially if the bike is going to be used for heavy loads/touring, as they are, reputedly, stronger.

 

[fasturtle]

If the budget allows its nice to go to freehub, especially if the bike is going to be used for heavy loads/touring, as they are, reputedly, stronger.

I am using it for long rides. Where I live is hilly so I find the extra gears help. I was looking at upgrading instead of buying new. I tried a 17 inch frame the other day and the reach was further away than my current bike which is a 19 inch. I have some Dutch handlebars coming which should help my sitting position so I thought I might try upgrading the gears as well.

 

[fossyant]

Probably easier to go 8 speed,assuming the back end is 135mm spacing - see above.

Lots of new 8 speed shifters and mechs available.

 

[Blue Hills]

Probably easier to go 8 speed,assuming the back end is 135mm spacing - see above.

Lots of new 8 speed shifters and mechs available.

yep or even 9.
more choice of bits/cassettes etc, particularly cassettes that are good for hills. 34T big cog on 8 speed pretty common, 9 speed has the wondrous 12-36.
Lots of 8 speed and 9 speed shifters available on the bay as well - lots of 7speed shifters seem to be combined with the brake levers - a bad idea I think.
(wouldn't go any further)
as you say depends on back end - I have the idea that by the time 7 speed came in on MTBs/hybrids, 135 was common.

 

[cyberknight]

i agree with the above , its a lot of work to gain 1 extra gear at the back.
another option would be to get a wide range freewheel to give you the lower gears for thr hills whilst keeping your existing set up

 

[fasturtle]

Thanks everyone. I didn't think 8 or nine would be an option. Lots to think about.

 

[Blue Hills]

Thanks everyone. I didn't think 8 or nine would be an option. Lots to think about.

i would say if you can get to 7 OK you can probably get to 8 or 9 fairly easily.
(someone more techie feel free to correct me).
I've taken 3 nice frames from 7 to 8 or 9 - changed cantis to V brakes - separate gear and brake controls.
9 speed - you can get some nice trimmable rapidfires which are handy for bodgery.

 

[sleuthey]

Most of the cheaper 6 speed free wheels iv seen only go as wide as 14-28T which limits the range for hills. If your going to go to the expense of replacing the wheel and shifter you may as well get a 9 speed shifter and fit a 11-34T or 12-36T cassette which are cheaply and widely available.

 

[Cycleops]

What frame is it? Steel or aluminium? Bear in mind you won't be able to 'spread' an aluminium one.
As above I should go for 9 speed if you can, plenty of SH stuff floating about at a reasonable price.
You might find this useful:

View: https://youtu.be/n5YkkAP_QVI

 

[Ajax Bay]

I didn't think 8 or nine would be an option.

I suggest it probably isn't (depends on your answer to steel v aluminium, and what you think of as 'old'. Bear in mind the average age of commenters here is (wild guess) over 55. An 'old' MTB will have an OLD of 130mm and a 'modern' (freehub) MTB wheel will not fit (135) and an alloy frame cannot be spread.
Keep it simple: just get a 7sp block screwed on and a RH 7sp shifter. The chain will work; the RD will work. Job done.
If you really need some 'silly low' gear (assume a 22t inner chainring) then how about a 14-34:
https://www.bikeparts.co.uk/products/shiamano-freewheel-7-speed-14-34-tz500?
https://www.rutlandcycling.com/part...eewheel-14-34-tooth-cassette/MFTZ5007434.html

 

[DCBassman]

An 'old' MTB will have an OLD of 130mm and a 'modern' (freehub) MTB wheel will not fit (135)

So long as it's a steelie, it will be fine. 130 to 135 can be done just by springing it apart by hand and letting it snap back. If weedy me can do that, anyone can.
The biggest problem in my opinion is that the best value supplier of wheels is no longer easily available, or if available not so cheap. Taylor Wheels.