# 20 inch versus 26 inch wheels



## jorgemartin (15 Jun 2011)

Hello, I have a HP Velotechnik Grasshopper (FX). I love this bike but I lag behind my partner when we ride together. She has a conventional 26 inch trekking bike (both of us have 1.75 inch wide tyres). I was considering swapping the Grasshopper for a Street Machine. The Street Machine has a 26 inch rear wheel and a 20inch front wheel. But... is it worth the effort? Would the speed difference be noticeable?


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## squeaker (15 Jun 2011)

jorgemartin said:


> I was considering swapping the Grasshopper for a Street Machine. .............. Would the speed difference be noticeable?


Can't say definitely (I have an OSS Grasshopper, not tried a USS Street Machine, but would have thought not. I would try some faster tyres on the Grasshopper first (e.g. Marathon Racers), before going to the hassle of a commercial bike swap, and if the latter I'd try and find a Speed Machine


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## ufkacbln (15 Jun 2011)

The problem is the gearing.

I have a Gekko with 20" and a Catrike with 26", and the latter is faster, but I tend to spin out on the Gekko which is what limits the speed.

My Street Machine is again faster than the Gekko, but slower than the Catrike.

The speed machine for acceleration and speed is the Catrike, but in second place is the 20" wheeled Challenge Hurricane which is faster than the 26" Street Machine... mainly due to the custom 65 tooth chain ring which raises the gearing.


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## arallsopp (15 Jun 2011)

Agreed. Gearing and rubber is the only real difference. My Streetmachine takes more effort than the Furai to get to 26mph, but tops out a tad faster. They have similar input gear ratios, so the extra 2" diameter comes into play.
Put a dinner plate on the front of your grasshopper, and it'll be largely identical to its big sister.


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## jorgemartin (15 Jun 2011)

If I get a bigger chainring, I'll go substantially faster? Is this a particular kind of chainring? How do I get one? By the way, I have the SRam Dual Drive gearing system.


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## arallsopp (15 Jun 2011)

What do you have at the moment? I'm guessing an 11-34 rear cassette, 3 speed hub and 42T front. The single ring at the front is easy to replace as you don't need to worry about ramping pins, derailleur angles and capacities.
Any single speed chainwheel with the correct BCD will probably fit. You might need to lengthen the chain a little if adding a lot of teeth.
In terms of speed, yes, if you can pedal at the same speed, you will go faster.
The above gearing is the stock config for my 26". I find it way lower than needed. The dual drive gives a massive range, so I haven't bothered to change mine.


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## jorgemartin (15 Jun 2011)

Yep. My current set up is 11-34 and a 42T front chain ring. Should I go for a 48t?


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## arallsopp (15 Jun 2011)

Two questions:
- what's your target cadence- what's your target top speed
With those known, and a squizz at sheldon brown, you'll know the size you need


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## jorgemartin (15 Jun 2011)

Hmmm, not sure what target cadence is... or top speed for that matter. I'd be happy going 15% faster so I can keep up with my girlfriend's bike.


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## arallsopp (15 Jun 2011)

Well, yes, 15% more teeth will do that


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## Riding in Circles (16 Jun 2011)

What is the engine like?


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## jorgemartin (19 Jun 2011)

I went to my Local Recumbent Shop and they told me that I had two options:
- Upgrading to a 52T chainring = £78 (13% more efficient than what I have now)
- Upgrading to a 60T chainring = £178 (30% more efficient)
The second option is a lot more expensive because it involves replacing the whole crank set. My current set up is is a 46 T chainring (not 42 as I thought) a 5 bolt 110 mm BCD (the 60 T chainring is for 130 mm BCD) (and the SRAM dual drive with a 11-34 rear cassette).
These parts come from HP Velotechnik and have a safety ring or guard. The guy from the shop told me that these are mandatory. 
I was thinking of sourcing a chainring from another place but I don't seem to be able to find a chain guard that is large enough to accommodate 52-60 T chainrings. 
Any ideas/suggestions?
PS Is a bigger chainring going to make it more difficult to go uphill? 
ie 52T chainring= 13% more difficult?


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## Night Train (19 Jun 2011)

Anything that riases the overall gear ratio will make it harder to climb hills.

Maybe what you need is to wident he gear ratios by increasing the top end without losing the bottom end.

Could you switch to a double front chainring with a deraileur? You can then have your larger chainring for speed and the smaller one for hills.

I added a triple to the front of my old Ratrike and it is is a lot more 'useful' to have 'faster' and 'slower' gears.


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## arallsopp (19 Jun 2011)

First, if your local recumbent shop said a big ring was more 'efficient', their advice can probably be discarded.
Second, I'm not aware of any legislation in the UK mandating a chainring guard, outside of HPV racing. Neither of my 'bents has a guard on, and one is a 2008 HPVelotechnik in stock configuration.
For that money, you might want to look at a capreo hub, or a TA / Stronglight chainring, which tend to come in a variety of sizes.


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## jorgemartin (19 Jun 2011)

So speed and efficiency are different things? If having a chain guard is not mandatory, then I don't see why I need to source a super-expensive chainring from HP Velotechnik... Is there anything to be aware of when I buy a new chainring? Does it have to single speed? Having a double chain wheel is a good idea, but involves a lot of work and expense... Perhaps having a 3 speed hub plus a 8-9 speed cassette plus a front derailleur is an overkill?


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## Night Train (19 Jun 2011)

Speed and efficiency are different.

Efficient is getting the most out from what you are able to put in. Speed is being able to put more in to get more speed.

In other words, if it was efficient you would be able to ride further for a given number of cakes.
If it was faster then you might get lots more top speed for short moments but burn out your legs and need more frequent cake stops.

Overkill would be 3x9 at the back with a triple and Schlumph drive at the front giving 162 gears.

The other way would be to have a bigger single chainring at the front but change the bottom gear sprocket on the cassette for one with more teeth. It will just give you a bigger step between 1st and 2nd on the cassette but you will be able to maintain a low gear for climbing.

Depending on your reach you could have a double or triple chainring, without the mech and just throw the chain manually with the guide tube if there is one. I do that on my Ratrike as the deraileur isn't cooperating at the moment.


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## StuAff (19 Jun 2011)

jorgemartin said:


> So speed and efficiency are different things?


Just posted this, then saw Night Train had summed it up better than me....

Before buying a load of expensive parts, you'd be best off working out how fast you're actually going now (buy a decent bike computer), and squeaker's suggestion of fitting some quicker tyres is a good one- certainly a lot cheaper than £180 for a chainring! Training is likely to do you more good than a bigger ring.


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## jorgemartin (19 Jun 2011)

Thanks everyone for the thoughtful replies. Hmmm. Having come across these concepts for the first time ever, I think I'm starting to understand speed, efficiency and cadence. When my girlfriend and I ride together and I'm using my 'normal' 26 inch wheel touring bike, we ride at a similar pace. When I ride the recumbent, I lag behind. I assume that my cadence must be the same on both bikes so it's probably safe to reason that I need a bigger chainring... However, I'm going to look up my cadence on the bike computer. and I'm definitely getting faster tires (the Marathon Green Guard tyres seem to be a good compromise between speed and durability as far as touring goes, the racer seems a bit flimsy for touring). I'm going to look into this cadence thing and perhaps I'll get a 52T or a 53T chain ring.


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## Night Train (19 Jun 2011)

The better, lower rolling resistance, tyres should give you a benefit whatever else you do or don't do. Even the same speed would be easier, or more efficient.

Checking cadance will tell you what you are putting in and you should then be able to see what gearing you can go to to get a bit more speed.

I found with my Ratrike that although with gearing I could get a good head of speed, 25+mph, downhill the thing holding me back was drag in the tyres, bearings and brake discs. I would have to work where others were coasting or even rolling down small down slopes.


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## arallsopp (19 Jun 2011)

You're Tufnell Park/Camden area, right?
Not far from a "Sunday London Ride", if you want to hook up and talk these things.


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## jorgemartin (20 Jun 2011)

Yes, I'm in Tufnell Park/Camden. Is Sunday London Ride a recumbent event?


arallsopp said:


> You're Tufnell Park/Camden area, right?
> Not far from a "Sunday London Ride", if you want to hook up and talk these things.


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## recumbentpanda (20 Jun 2011)

Cadence is a very individual thing, and depends a lot on what legs you were given and your pedalling style. Speaking VERY generally however, it tends to be the case that a higher cadence is more effective on a recumbent. It's effective on an upright too, but on a recumbent its often more necessary. This is because you don't have the advantage of being able to use upper body muscle groups by pulling on the bars, and because 'bench-pressing against the back of the seat tends to cause pain in knee ligaments for most people.

Think of it like a car with a small engine. You get best performance by giving it lots of revs. My sister had an old Citroen Dyane. She was amazed one day when I drove her in it over a hilly route, at how fast it could go up the hills. The difference in our driving styles was that I was really stirring the gearbox and using lots of right foot to make sure that little engine was spinning at the high revs in which it is most efficient.

Same with your bent, try this experiment next time out with the GF: if you find yourself dropping back, drop down a gear and spin the pedals faster. Be prepared to change gear more frequently than on an upright to maintain cadence.

Having said that I've given up trying to chase my other half on any kind of bike. I've had to accept she's just a lot stronger than me!


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## tongskie01 (20 Jun 2011)

recumbentpanda said:


> Cadence is a very individual thing, and depends a lot on what legs you were given and your pedalling style. Speaking VERY generally however, it tends to be the case that a higher cadence is more effective on a recumbent. It's effective on an upright too, but on a recumbent its often more necessary. This is because you don't have the advantage of being able to use upper body muscle groups by pulling on the bars, and because 'bench-pressing against the back of the seat tends to cause pain in knee ligaments for most people.
> 
> Think of it like a car with a small engine. You get best performance by giving it lots of revs. My sister had an old Citroen Dyane. She was amazed one day when I drove her in it over a hilly route, at how fast it could go up the hills. The difference in our driving styles was that I was really stirring the gearbox and using lots of right foot to make sure that little engine was spinning at the high revs in which it is most efficient.
> 
> ...



no power gained pulling on the bars. shifting the body weight forward while going uphill is what does it.


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## jorgemartin (21 Jun 2011)

I think I've considered tried all kinds of things but I'm going to give this a mindful try.


recumbentpanda said:


> Same with your bent, try this experiment next time out with the GF: if you find yourself dropping back, drop down a gear and spin the pedals faster. Be prepared to change gear more frequently than on an upright to maintain cadence.


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