phtomita

Almost there, one more post and you are able to attach a pic!

BlazingPedals

Careful! Some of the Shimano cranksets use a proprietary bolt pattern instead of the usual 5-arm. If the Origin8 doesn't work because it's not that proprietary pattern, then you're stuck using Shimano if you're set on re-using the rings. The crankset doesn't have to match the cassette.

Leisesturm

Hmmm. There is enough argument that the seat should be raised 1/2 the difference of the amount of the new crank-length as argue that the seat should be raise the full amount of the difference in crank-length to make your opinion ... open to further opinion. I see the validity of both sets of arguments. Myself would chose to raise by 1/2 the amount of the difference: 5mm. IOW, also counter to your own opinion. And there lies the RUB. 5mm is less than 1/4". An amount that is just about perceptible to normal hands and fingers but IMO virtually imperceptible to gross lever systems like the calf/thigh/ankle interdependence. That is why I advised the o.p. not to bother with the crank swap. But IF s/he were to proceed, IMO nothing more than 150mm as the new crank-length should be considered. In theory the gears should be lowered a corresponding amount. Practically, that is impossible because the o.p. is already running a 50/34 compact crankset with no practical downward extension and her cassette is probably the ubiquitous 11-32 and the rear derailleur spec'd to work with that. Gear selection becomes self-limiting and it is up to the cyclist to favor lower ratios when they have gone over to shorter cranks that reduce the amount of torque that they can supply vs before the crank swap.

Olgaimage

BlazingPedals: my bike uses the 5-arm. I showed the bike mechanic the Origin8 pedals, and he said that they fit although they are JIS. However, I'm afraid of buying them because someone has written a bad review on Amazon and posted pictures of one of the arms broken into two halves, and he writes that he has bought the crank arms twice and it happened both times. About the cassette: Another bike mechanic told me that if I have 2x8 speed then the crank has to fit that. Sorry if the "speed" is not the same as the cassette.

Leisesturm

It will be impossible to use the Origin 8 arms if you have a spindle with a different taper. What brand is the crankset? If no branding then it is safe to assume JIS taper. BB shell? Easy to measure. As you know I really doubt this change will be of benefit. I might feel differently if you had bought a name brand road bike of sufficient value to make the investment of more money and labor worth it. OR if you didn't have to rely on paid LBS labor to accomplish it. Do you have non-profit bike co-ops in your area? It might be worth taking your bike to one of them because standard shop rates are $62/hr. and higher in my area. Bike co-op labor rates are often half of that or less. They also might have cranksets that could work at nominal cost. I see no evidence that the Origin 8 cranks are drive side only. You will get both cranks. But as Blazing Pedals observes they will be heavy. Their longevity is open to question. I don't know if they have a 150mm option, but they do have a 155mm. I'm big on the "go big (small), or go home" mantra of magnitude of change. Especially when big money is on the line and the amount of money spent is identical regardless of the end result. FWIW

Olgaimage

It makes me sad that you want to convince me not to buy them. Other people have also told me that it doesn't matter and I shouldn't do it. But I really want to help my knee. I have been seeing a PT for 6 months and I just had an MRI scan. I only use 2nd, 3rd and 4th gear (not sure if it is the correct way to say it) and I try to avoid hills. I have read an article written by a bike fitter who states that crank arm length is very important and that he and his customers have benefitted a lot from getting shorter crank arms, even just 5 mm shorter. In the article, there is a formula in which you can put your inseam and your "greater trochanter height" and then you get your perfect crank arm length. Mine is 156.6 mm, so 155 mm would be better for me I guess, but I am afraid of buying them so short. I e-mailed the bike fitter and he said that either one of them would be fine for me.

I don't know what a non-profit bike co-op is. It seems impossible to get a 160 mm crank arm in Denmark where I live.

My crank set is FSA.

Someone else in this thread said that my bike probably has an ISO BB because it is the European standard. But my bike or at least some of it is made in Taiwan so maybe it has the other one.

phtomita

Post some pics of your bike and everybody will be in same page
Bike overall on driver side, close up of the crank, bottom bracket area.

Leisesturm

I am sorry that it makes you sad that I am neutral to the idea of your swapping out your crankset. I am happy however that I am not the only one who has advised for the same thing. I guarantee that if you give that 200 Squat program a try that by week 4 you will notice a marked improvement in both knees. Knees are fixed by PT off the bike. FSA bottom brackets are JIS taper. Denmark is a very bike aware country. Maybe you don't need co-ops there but in the United States both what we call LBS's (local bike stores) and bike co-ops (501C3 not for profit corporations) exist side by side to meet the needs of the cycling community. LBS's mainly sell new bicycles from major manufacturers and service the bikes they sell at a discount and other major brands at the earlier stated labor rate. Bike co-ops mainly sell reconditioned bicycles and service all bikes at a reduced labor rate. Sometimes for no charge, often while you wait! If your formula says to get 155mm cranks why are you looking for 160mm? Either you believe that the shorter crank can help or you don't. It does no good to hedge your bets and get a crank not quite short not quite long. "Go big, or go home". In other words, make a change big enough that you can notice whether or not it helps.

Olgaimage

Okay, nice to know that it is JIS.
I will consider getting 155 mm crank arms
I have tried doing squats but it is too hard for my knee. I have an irritated fat pad, I don’t know if you know anything about it.

Olgaimage

If I want 155 mm crank arms, I'll have to buy the Origin8 in silver. Another option is Sinz arms: https://www.ebay.com/itm/Sinz-Expert...8AAOSwjthcL6HE
But it doesn't say whether it needs a JIS BB or an ISO BB and what speed it works with.

veganbikes

I would go talk with an actual fitter first. An article is all well and good but actually getting a fit is going to help you out way way more. Playing guessing games in this situation doesn't sound like the right move. If you are having knee pains a good fitter can help you with that and maybe a shorter crank might be a suggestion but there might be many other things that could be causing knee issues on your bike that can be fixed without swapping cranks.

Plus the fitter will likely have recommendations on parts to get to achieve the correct fit and might even stock some of that stuff so you can get more comfortable on your bike.

Leisesturm

As I understand it, the only ISO system remaining is Campagnolo. All others are JIS. I don't think you need to worry about 'speeds'. The 110mm bolt circle means one or two rings only. The only other system is the triple which carries an additional set of bolt holders usually at the 74mm circle diameter for a 5 arm crank. You have an 8sp cassette. You already have 8sp chainrings and chainring bolts from your existing 50/34 setup. The chainring bolts that you have will keep the rings the proper distance apart for your 8sp chain to work. You are good to go.

MikeyMK

It's not really opinion though, is it. The bent leg is irrelevant for reach. Your straight leg is the definitive aspect with regard to leverage, power and comfort, in which case a crank arm shift requires a saddle height shift of the same measurement, either way, to maintain the optimum state of the push-leg. Having the non-push leg raise less, merely increases efficiency as a bonus by-product.

Olgaimage

That is good advice. I feel that I cannot place my right foot comfortably on the pedal (it is my right knee that is injured), maybe they can help me with that. I think it is because my thigh is not parallel with the frame but slightly turned outwards, as the pedal is placed a bit away from the frame because of the crank. As my leg is turned outwards, my foot is also turned outwards, so my heel hits the crank arm while I’m pedaling. This problem may be fixed with shorter crank arms, as there will be more space for my heel. Then their eventual other changes to my bike maybe won’t be needed anymore. I guess I could need their help first finding a fitting crank arm length and then letting them see again to see if I need other changes, but it is so expensive

veganbikes

A bike fit seems expensive but if you aren't comfortable on your bike and have a lot of issues with it a fit is well worth it.

shkimjohn

Did you end up getting a bike fit? I am 155cm in height and just recently got the Origin8 145mm triple crank and it definitely feels much more natural and comfortable than the 165mm cranks I was using previously.

Olgaimage

I did, I got to try different crank arms on a stationary bike, and I liked 155 best. I got it and now I can do hills that I couldn’t do before. I’m thankful for the help I got from this forum, I didn’t expect that so many people would reply.

Korina

Any chance you could post a pic of your bike?

I also have a short crankset that my husband keeps promising he'll install; until then, I'm stuck with a 29" inseam and 175 mm cranks.

MikeyMK

'5x110 bcd square taper', now we're getting somewhere - that's all you need, and you can use your current 50/34t chainrings. Such arms are availavle for BMX or in kid's sizes, a quick look finds me this on the first page, so there must be quite a few in the shorter sizes...

Litespud

That’s not correct - going from 170 to 160 means that the pedal is now 10mm higher at the bottom of the stroke. Therefore, to maintain the same leg extension at the bottom of the stroke, the saddle will have to come up 10mm. It also means, therefore, that the saddle-pedal distance at the top of the stroke will now increase by 20mm, meaning a significant decrease in knee flex at the top of the stroke, which is what the OP is going for, I think.

Olgaimage

Korina

@Olgaimage, sweet ride, thanks!

Olgaimage

Thank you