Question about front gear swap.

Question about front gear swap.

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E-bmw

Original Poster:

10,651 posts

164 months

Tuesday 21st January
quotequote all
Hi all,

Mrs E has an old-ish Raleigh MTB but suffers with not having low enough gears.

She has 5 on the rear & 2 on the front.

The front selector just shows low to high & doesn't really have actual click-stops for each if that makes sense.

My question is can I just fit a new front set with 3 gears & adjust the selector to go between these or is it not that simple?

If it is indeed possible are there different types/fittings etc?

I haven't counted the teeth yet, but was going to stick with the current spacing going down by a similar number of teeth for the lower ratio.

Thanks in advance.

jfdi

1,168 posts

187 months

Tuesday 21st January
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Unless it's really old the front gear shifter (at the handle bars) will control the 2 positions of the front mech (the part that moves the chain across). You can't just switch to a triple front ring as your shifter can only handle 2 positions.
Even if you sort a new 3 position shifter you will also need to ensure the rear derailleur has enough movement to take up the extra slack in the chain caused by the lower gear.

E-bmw

Original Poster:

10,651 posts

164 months

Tuesday 21st January
quotequote all
OK, thanks for the tip, I will have to see if I can find out a bit more as you say first then.

Gin and Ultrasonic

268 posts

51 months

Tuesday 21st January
quotequote all
As said above, changing from 2-3 rings at the front will also need new shifters at least, and various possible adjustments at the back, which may or may not work.

The general 'easy' options for lower gearing are to stay within your existing '2 at the front, X at the back', which means you don't have to change shifters, gear pull ratios and all sorts of stuff that can get complicated and pricey.

Options -
New cassette with bigger largest sprocket - depending on how much bigger, it might need a new derailleur at the back too.
and/or
New front chainring with smaller sprockets - e.g. going from 40/26 to 36/22.

A new cassette would generally be the cheapest option. It probably depends if you're looking for a slightly better 'easiest gear' (cheap) or a significant change (not cheap).


E-bmw

Original Poster:

10,651 posts

164 months

Tuesday 21st January
quotequote all
Gin and Ultrasonic said:
Options -
New cassette with bigger largest sprocket - depending on how much bigger, it might need a new derailleur at the back too.
and/or
New front chainring with smaller sprockets - e.g. going from 40/26 to 36/22.

A new cassette would generally be the cheapest option. It probably depends if you're looking for a slightly better 'easiest gear' (cheap) or a significant change (not cheap).
OK, so (I stress I need to have a closer look when I get it home as it is currently on the back of our motorhome, having just been away for the weekend) would it be possible to do a combination to hopefully negate the chain/derailleur issues?

As in down a bit on the 2 front & up a bit on the rear set?

Gin and Ultrasonic

268 posts

51 months

Tuesday 21st January
quotequote all
I think in general the smaller the change, the more likely it is to work without further changes. Everything will have a spec and maximum range (e.g. a rear derailleur might take a cassette with a max of 34 teeth, with 36 being possible at a push), so it's really hard to say exactly what will and won't work.

I've never replaced chainrings myself but I think they may need tweaks to the position of the front derailleur if they are smaller, as it will not be able to change as well if the chain is in a different place (lower down).

It might be worth having a chat with a local bike shop to see what's possible - with it being an older bike the options / parts might be more limited, but they should be able to advise what your options are and how much it's likely to cost.

InitialDave

12,903 posts

131 months

Tuesday 21st January
quotequote all
If it has a friction shifter for the front derailleur, I suspect it really is rather old, and there's a good chance it has an old screw-on freewheel rear end rather than a cassette design.

That doesn't preclude changing things, but it does affect what might be optimal and cost effective.

Bikes have a hilarious amount of the principle "the great thing about standards is there's so many to choose from", it may help to have a least a couple of pictures of the bike/drivetrain to let people give you more targeted advice.

OutInTheShed

10,606 posts

38 months

Tuesday 21st January
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The parts to change it to 8 speed on the back with a wide ratio cassette should be pretty cheap secondhand or even new.
Come to that, a reasonable used bike with 'enough' gears should not be expensive or hard to find.

HenryV1415

1,276 posts

232 months

Wednesday 22nd January
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If it’s 2x5 speed then the bike will be so old and delaminated with a poor geometry and fit that the kindest thing you can do is buy your wife. A new bike. It’s absolutely not worth upgrading. Nobody gets enjoyment from a crap heavy, ill fitting bike. She will just decide she hates cycling.

E-bmw

Original Poster:

10,651 posts

164 months

Wednesday 22nd January
quotequote all
HenryV1415 said:
If it’s 2x5 speed then the bike will be so old and delaminated with a poor geometry and fit that the kindest thing you can do is buy your wife. A new bike. It’s absolutely not worth upgrading. Nobody gets enjoyment from a crap heavy, ill fitting bike. She will just decide she hates cycling.
Thanks for all the replies guys, I will look into it further & see if any of your suggestions are possible.

Henry,
When I got my bike a couple of years ago I did suggest to her we change hers, but (bless her) she doesn't see any need to get rid of something that just works.

If I can make it better for her (the times that she feels the need to get off & push are very irregular) I will, if not I will keep pushing her until she agrees with this.

Thanks again everyone.

InitialDave

12,903 posts

131 months

Wednesday 22nd January
quotequote all
On that basis, there's no practical reason why you couldn't add a triple chainring at the front and have it work with the friction thumbshifter, though it's possible you may need more derailleur range/capacity to deal with the wider spread of potential gears, and if replacing the crankset, the bottom bracket axle length may need to be different to get the chain line right.

Again, pictures of what you're starting with would help a lot, and while I understand her not seeing the need for new bike, it is quite possibly the most sensible option even if not the cheapest.

E-bmw

Original Poster:

10,651 posts

164 months

Wednesday 22nd January
quotequote all
InitialDave said:
On that basis, there's no practical reason why you couldn't add a triple chainring at the front and have it work with the friction thumbshifter, though it's possible you may need more derailleur range/capacity to deal with the wider spread of potential gears, and if replacing the crankset, the bottom bracket axle length may need to be different to get the chain line right.

Again, pictures of what you're starting with would help a lot, and while I understand her not seeing the need for new bike, it is quite possibly the most sensible option even if not the cheapest.
Gottcha, I will upload a couple of pics when I get eyes on it later in the week.

On the subject of a new bike, have you ever tried explaining "man-maths" to your good lady?

InitialDave

12,903 posts

131 months

Wednesday 22nd January
quotequote all
E-bmw said:
On the subject of a new bike, have you ever tried explaining "man-maths" to your good lady?
I, for my sins, have zero management in place, which sounds delightful but is bloody dangerous for my impulse control.

E-bmw

Original Poster:

10,651 posts

164 months

Wednesday 22nd January
quotequote all
InitialDave said:
E-bmw said:
On the subject of a new bike, have you ever tried explaining "man-maths" to your good lady?
I, for my sins, have zero management in place, which sounds delightful but is bloody dangerous for my impulse control.
I have lived far too many years like you & keep forgetting the need to justify expenditure to A.N.Other. wink

Super Sonic

8,761 posts

66 months

Wednesday 22nd January
quotequote all
InitialDave said:
On that basis, there's no practical reason why you couldn't add a triple chainring at the front and have it work with the friction thumbshifter, though it's possible you may need more derailleur range/capacity to deal with the wider spread of potential gears, and if replacing the crankset, the bottom bracket axle length may need to be different to get the chain line right.

Again, pictures of what you're starting with would help a lot, and while I understand her not seeing the need for new bike, it is quite possibly the most sensible option even if not the cheapest.
A front mech designed for a double chainring crankset is extremely unlikely to work with a triple. The mech will not have enough swing or capacity. That's without taking into account the need for a rear mech with a higher capacity.

E-bmw

Original Poster:

10,651 posts

164 months

Friday 24th January
quotequote all
Well that was a complete waste of every bodies time time & effort.

Got the rear end apart, checked what I could, researched what I could & came to the point of closing in on a solution, so just went to ask which gears it is she uses.

"Oh, I only ever use 1, 2 & 3"

"Is that low or high ratio?"

"????????"

Cue 30 minutes of trying to explain low/high/1/2/3/4/5 etc.

"????????"

Sometimes I wonder if as men we talk a completely different language!

I am just going to swap her front cogs for slightly smaller & not tell her, it is definitely the easiest solution.

Master Bean

4,279 posts

132 months

Friday 24th January
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My mum has a 3 x 8 bike. She doesn't change the front gear. Stays in the middle and just changes the back gears. Works fine for her use profile.

POIDH

1,505 posts

77 months

Monday 27th January
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Best thing my OH did was go to a widerange 10sp with single chainring...