UKH

E-bike question 3

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Mrs W's new E-bike comes with a Shimano double chainset 50/34, which leaves me spitting blood. To start with, anyone who needs electrical assistance on a bike does NOT need a 50x11 top ratio giving a 120 inch gear! In my mis-spent teen years doing time trials my top gear was 96 inches, which included just missing 2 hours for a 50. And then the size of the drop/increase in cadence when  changing from one ring to another is really annoying. And then the gears you're most likely to want are either clustered at the small side of the cassette when on the 34 or near the large side when on the big ring. Much better to have a smaller big ring (42 or 44) which you'd be on most of the time and using the front and rear pairings with the best chain alignment. Idiotic!

When you look at the numbers of older folk cycling, I can't understand why the manufacturers don't cater for our needs.

My local bike shop tells me there is no alternative set up because the classic Stronglight/TA cranks and rings (which would be perfect) require a different BB which won't fit the bike. Clutching at straws, but does anyone have a solution? 

 JLS 15 Aug 2019
In reply to Rog Wilko:

I’m not sure how I’d have coped in my racing days with the bigger jumps between gears but now I’m comfortable with “just going slower” to keep the cadence right.  

Would a close ratio JUNIOR cassette help?

14-15-16-17-18-19-20-21-23-25-28

I think they may also come in 16-up too.

Frankly, I think you are just trying to hobble the Mrs so you down get dropped on long downhills when she fires up the motor in the 50x11.  

In reply to Rog Wilko:

Don't know why anyone puts more than a single on ANY bike.

 wintertree 15 Aug 2019
In reply to blackmountainbiker:

> Don't know why anyone puts more than a single on ANY bike.

Reverse.

In reply to wintertree:

Single/single? A fixie? 

In reply to wintertree:

Single up front/12 at rear.

In reply to JLS:

> Would a close ratio JUNIOR cassette help?

> 14-15-16-17-18-19-20-21-23-25-28

Probably not as I don't think a 34x28 is really low enough. Needs to be 10 speed anyway.

> Frankly, I think you are just trying to hobble the Mrs so you down get dropped on long downhills when she fires up the motor in the 50x11.  

No, it's uphill she's dropping me now. You're perhaps forgetting that ebike motors cut out at 15 mph. I can still drop her above that speed.

 wintertree 15 Aug 2019
In reply to blackmountainbiker:

> Single/single? A fixie? 

It’s traditional to have a lower gearing in reverse.  My car is single gear for forwards and it’s still got a lower ratio for reverse.

 boriselbrus 15 Aug 2019
In reply to Rog Wilko:

From the Ribble website I can't tell what BB is on the bike, but it uses a Shimano chainset so will be either a press fit or external screw in BB with a 24mm axle.

You can go for a Shimano GRX 600 chainset with 46/30 rings available on Wiggle now.  It is 11 speed but will work fine.

If you tell me what BB is on the bike - even post a photo - then I can find some other options.  But there are definitely options depending on what rings you actually want.

 FinrodFelagund 15 Aug 2019
In reply to blackmountainbiker:

> Don't know why anyone puts more than a single on ANY bike.

For touring I have a triple 50-40-26 up front and a 32-12 at the back. That gives me a range from 50/12=4.17 to 26/32=0.81

You won't get that with a single chainring.

 top cat 15 Aug 2019
In reply to Rog Wilko:

Surely you just remove the offending chain rings and fit what you want?   Inner 42 or 44 then maybe a bash ring outer so that the chairing bolts still work, other wise you will need a special washer or shorter bolts?   

I've converted a number of triple cranksets to either double or single.  Easy job.

In reply to FinrodFelagund: But a 40 paired to a 10-52 would give you 4 and 0.77 which is pretty close.

 IainL 15 Aug 2019
In reply to Rog Wilko:

The manufactures have tried to sell lower gears but the purchasers want what the pros use. Boardman came out with low gear sets originally but they did not sell. I use Spa Cycles to get the chainsets I want, plus a lot shorter cranks.

In reply to wintertree:

A. It's a car

B. A single gear for forwards? Are you the person I always get behind on the way home from Brecon not going over 15mph?

 wintertree 15 Aug 2019
In reply to blackmountainbiker:

> A. It's a car

Pretty sure I’d want a lower gear for reversing my bike - I can’t really see where I’m going.

> B. A single gear for forwards? Are you the person I always get behind on the way home from Brecon not going over 15mph?

Nop.  A lot of electric vehicles only have a single forwards gear.  Top speed of our Leaf in reverse is rumoured to be about 50 mph but I haven’t had the inclination or spare runway to try it out...

In reply to wintertree:

Ah, electric. Never tried reversing my bike, apart from failed technical climbs but that's involuntary. 

In reply to boriselbrus:

Thanks for your very helpful reply. It is a press fit BB. The bike spec. says Shimano OEM BB71 Press fit 86.5/41mm if that helps. I could email you a photo, but this may be enough.

I am assuming the GRX 600 chainset is meant for MTB. It is a possible solution I was going to look at next. The 46-30 rings isn't ideal for my purpose, but it might work, Mrs W could then use the 46 ring most of the time and just bring in the 30T on steep hills. My other concern might be if the front changer could be adjusted enough to accommodate the smaller rings. Going to have look at that next.

Are there any compatible rings of different sizes, do you know?

Would I be able to use my existing chain (10 speed)?

In reply to Rog Wilko:

What is the bcd on the chain rings?

 boriselbrus 15 Aug 2019
In reply to Rog Wilko:

No worries - it always intrigues me on here when someone asks "What chainset can I use" and they get an answer of "My car will do 50mph backwards"!

Anyway, the GRX chainset is designed for Gravel bikes - basically drop handlebar bikes with wider tyres for riding gentle off road.  So it is fine for use with the shifters you get on drop handlebar bikes.  Your existing chain will be fine - 11 speed rings are very slightly thinner than 10 speed, but you'll never notice any difference.  You could shorten your chain by a couple of links, but again, if you don't you'll never notice.

You may be just able to change the chain rings of your existing chainset, in the old days you'd just get some rings with the same BCD (Bolt circle diameter) and bolt them on.  But now some chain rings have an off set - 2 of the bolts are closer to the centre of the cranks than the other 2, so finding compatible rings is no longer so simple.

Your existing from mech will almost certainly work.  You will probably have to drop it down by around 5mm for shifting to be optimal.  If you can't then the shifting may be a bit noisy and if you use the small chain ring and the smallest sprocket combinations the chain will probably rub on the lower part of the mech cage.

The press fit BB does slightly limit your choices.  If you stay with Shimano cranks then there is no problem, Wiggle do have a 105 CX50 chainset with standard 110BCD rings so you could get that and fit the rings of your choice to it. It comes with 46/36 as standard.

In reply to blackmountainbiker:

> What is the bcd on the chain rings?

Don't know.

In reply to Rog Wilko:

BCD is the distance between the centres of the opposite chain ring bolts. If you can remove the chain rings you will be able to pick up a cheap narrow wide ring from eBay and some spacers and a wide range sunrace  cassette. 

In reply to boriselbrus:

I don't think the Tiagra chainset will take any other rings. The rings and spider are held together by bolts inserted from the inside of the small ring and the bolts go into threaded holes on the inside of the large ring. I think.

I've looked at the front mech mount and I think it will move down about 10mm, which should be enough. The 105 chainset looks like a possibility. Looking at the pictures I'd guess 36 is the smallest possible inner ring.

Thanks for your help.

 boriselbrus 15 Aug 2019
In reply to Rog Wilko:

Yes the Tiagra chainset is as you describe - you may be able to get smaller rings to fit it but I'm not aware of any.  That renders the BCD question irrelevant.  You also won't be able to get a narrow / wide single ring for it.

BTW I wouldn't go down the single front ring route anyway.  It's pointless on this bike - you don't save any weight as you have to keep the shifter, you lose the weight of the cable and front mech and one ring, but add the weight of a huge cassette and you'll need a new rear mech as the existing one won't cope with a 50t cassette without bodging.  Also whilst you can get the same gear range, with only 10 gears you'll have huge gaps between gears.  OK on a MTB, but horrible on the road.  I get 1x systems on MTB's - better mud clearance, frame design not limited for suspension etc but for road use where you can be climbing at 5kph one minute then descending at 80kmh the next, there really is no benefit.

In reply to boriselbrus:

I'm moving towards your suggestion of the 105 CX50 with the 46/36 rings. You mention being able to get different size rings to fit, but I haven't been able to find these. Can you point me in the right direction for those? The 46/36 wouldn't be unacceptable but something a bit smaller would be preferable. There's another question related to all this - the Tiagra rear mech is the long cage version which means I could probably get the 11-34 cassette working, but 2 teeth more only makes a smaller difference and I have seen an 11-36. Do you know if that works too? 

Thanks again for your advice.


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