Gearing advice

[ushills]

Hi, I've now returned to road cycling following 10years off MTB'ing, previously had a lot of experience with road racing/closed circuit etc.

However, with my Pinnacle Dolomite One i am finding the gearing a bit lacking, I generally have a high cadence, typically between 90-105rpm and do not like griding up hills as I am not exactly a lightweight 187lb.

My current gearing is an 8 speed, 12-25 shimano type W rear and a front double 42 and 50 tooth chainring (shimano 2300) and using Sheldons gear calculator this gives me a climbing speed of almost 12mph in the 42-24 at 90rpm and a top speed of 32mph on the flat using the 50-12 at 100rpm. Rarely do I naturally drop below 85rpm, however, anything above a 5% slope starts to get the breathing going as I try to maintain cadence and speed.

I generally find that I rarely go below 50-15 and the 42-25 is nowhere near high enough for hill climbing with my high cadence while seated, i'm trying to take it easier now!!

Anyway, any suggestions of how I can set my gearing up to be more suitable without spending a fortune, I can change all the parts myself but looking for ideas of what others use.

PS have a dodgy knee hence not willing to grind up the hills.

 

[Dave Davenport]

A 39 inner has the same bcd as the 42 so just changing that would be easy/cheap and give you a bit more. Or, change the complete chainset for a 'compact' maybe 36/50. You'd probably need a new bottom bracket as well.

 

[ushills]

A 39 inner has the same bcd as the 42 so just changing that would be easy/cheap and give you a bit more. Or, change the complete chainset for a 'compact' maybe 36/50. You'd probably need a new bottom bracket as well.

Thanks for the advice Dave, could I also reduce the 50 outer without consequence as I rarely/never use the 50/12. I will have a look for the ideal combination to give a decent range.

 

[Tigerbiten]

If your going to swop out the big ring then think about swopping down to the moutain bike range of rings.

You'll prob need new cranks, but the big ring will be in the 48-44 range and the small one aound 12-14 teeth smaller.
So work out with a gear calculator whats the top and bottom gears that you want.
Then workout what chainring + block combo gives you them.

Luck ..........

 

[Dave Davenport]

The crankset is 5 bolt / 130mm, you should be able to get outer rings down to about 46 teeth but 38 is the smallest inner it will take.

By the time you've bought two new rings which still won't give you a very low bottom gear you'd be better off switching to a compact imo. Have a look at;
http://www.sjscycles.co.uk/chainsets-road-dept888_pg1/#page=1&order=PRICE ASCENDING

 

[ushills]

I've now discovered that the smallest I can use on the outer is a 50T as per the shimano docs, so will try the 39T. Will it make much difference from the 42T.

 

[ushills]

The crankset is 5 bolt / 130mm, you should be able to get outer rings down to about 46 teeth but 38 is the smallest inner it will take.

By the time you've bought two new rings which still won't give you a very low bottom gear you'd be better off switching to a compact imo. Have a look at;
http://www.sjscycles...e=1&order=PRICE ASCENDING

Thanks for the pointers, think I have settled on on of these http://www.parker-international.co.uk/16483/Shimano-2350-8-Speed-Compact-Chainset.html as it appears to be a direct swap for what I've got but in a compact form.

Using Sheldon's gear calulator I am supprised to find that with my current setup I only really have 10 usable gears going from 44 inch to 110 inches, but the middle 6 of my 8 speed effectively overlap each other, I had noticed that when going from the outer to the inner I only needed to drop 2 gears at the back.

The 34-50 compact will give me from 35 inches to 110 inches and 12 usable gears, basically an extra 2 low gears that should help on the hills for just over 30 quid.

 

[ColinJ]

I've now discovered that the smallest I can use on the outer is a 50T as per the shimano docs, so will try the 39T. Will it make much difference from the 42T.

A given cadence will reduce your speed to 39/42 of what it would have been and it will take 39/42 of the pedalling force! (I.e. about a 7% change - significant, though not huge.)

When I made that change to my first bike, it was the difference between just failing to get up certain hills and just managing to, but they were still hard work. I had to change to a triple with a 30-tooth small ring to make climbing steep hills comfortable.

 

[ushills]

A given cadence will reduce your speed to 39/42 of what it would have been and it will take 39/42 of the pedalling force! (I.e. about a 7% change - significant, though not huge.)

When I made that change to my first bike, it was the difference between just failing to get up certain hills and just managing to, but they were still hard work. I had to change to a triple with a 30-tooth small ring to make climbing steep hills comfortable.

Alas a triple is out of the question as I cannot afford the upgrade costs, funnily enough the Dolomite One that Evans now sells comes with the 34/50 compact and it's still last years model.

Going from 42t to 34t (with the compact) will result in me needing only 80% of the effort to get up the hill so this should be okay and perhaps I can change that to something less that 34t but there are no product manuals on the Shimano site yet for the compact chainset (FC-2350), 20% less effort sounds good and that should get my cadence on the hills from the low 80's to above 100 and be good for my knees.

Thanks for all pointing me in the right direction, may be able to sell the original chainset as it's only done 100 miles.

 

[Dave Davenport]

Thanks for the pointers, think I have settled on on of these http://www.parker-in...t-Chainset.html as it appears to be a direct swap for what I've got but in a compact form.

Using Sheldon's gear calulator I am supprised to find that with my current setup I only really have 10 usable gears going from 44 inch to 110 inches, but the middle 6 of my 8 speed effectively overlap each other, I had noticed that when going from the outer to the inner I only needed to drop 2 gears at the back.

The 34-50 compact will give me from 35 inches to 110 inches and 12 usable gears, basically an extra 2 low gears that should help on the hills for just over 30 quid.

Looks like just the job.

 

[ColinJ]

Yep, looks good. Out of stock until December though ...

 

[fossyant]

42 x 21 used to be my lowest gear - those were the days (20 years ago) !