Round to oval question

Currently on a 34 round ring
Was going to change to a 30 round from a 34 round but fancy trying out these oval rings to help these old knees.
30 oval = 28 – 30 overall
32 oval = 31 round overall(more specific)
I run sram 11 speed cassette, will I run out of top end speed with the 30 oval?
I normally stay around the 3rd from smallest ring when going for it on flat trails.
What’s your experience of changing rings?

I run sram 11 speed cassette, will I run out of top end speed with the 30 oval?

no idea.

I swapped straight from 32 round to 32 oval. My experience is that it made my choppy pedalling a bit smoother.

Same went 32 round to 32 oval – it felt a tiny bit weird at first but then normal – can’t say it made anything easier or faster.

Biggest improvement was traction climbing in slop.

There’s still the same number of teeth on a 32T oval as on a 32T round so cadence doesn’t change for a given speed. What does change is the force required at different points in the pedalling stroke.

As P-Jay says: after a minute or two you don’t notice any difference except on climbs where you get better traction as the oval ring smooths out your awesome power.

so the anecdotal theory used to go, was that you could go up 2T from round to oval. So if you had a 30T round, you should get a 32T oval, which has something like 34-30 eccentricity. So in the bit where you struggled you were on a 30T effective for that part of the stroke or something. Certainly seems to be the case on my SS where I went from a 32T round to a 34T oval.

I’m not sure you can get a 30T oval unless you have specific cranks – my 32T oval on my 1×10 only just clears the tabs of the 104BCD, so a 30T (ie 28T smallest diam) would foul.

[edit – just looked it up and you can from Absolute but it needs special spacers and bolts]

If you can ride a 34T round (and I mean ride it, not suffer it), I’m not sure why you’d want to drop to a 30T given the above; I’d go for a 32T min and maybe even swap a 34T round for a 34T oval. Dropping to a 30T would reduce your available top end gears, your 34x 3rd (maybe a 14) = 2.4 corresponds to a 30T with your 2nd or even smallest cog depending on your cassette. Whether that’s an issue – only you’ll know.

Probably, yes. 30t oval and 30t round will result in same ground speed for a given crank rotation speed. 30×11 is pretty light for a high gear.

@theotherjonv – Absolute Black do a 30T oval that will fit 104BCD cranks, it has two normal bolts and two thinner ones with sleeves to prevent the fouling on the arms. If you want to go smaller than 30T then you’ll need a direct mount crank like the RaceFace AEffect which I have on my fat bike.

Oh, we don’t know what wheel size the OP is using, 34T on a 29er is pretty tough but would be OK on a 650b or 26″ wheel.

One other point – the eccentricity might cause the larger sizes to foul on the chainstay. My 32T oval ring only just clears the stay on my Solaris, a 34T oval would be a problem.

As above, felt weird for a few miles, then normal. Climbing steep loose stuff is where its of most benefit.

One thing i’ve found and not seen documented anywhere is it does make out of the saddle sprinting harder, i.e the oval timing is out when you shift position and try to sprint so you end up in the “dead” spots on the ring just when you need them. its something that Rotor must have realised and hence why they allow you to clock their rings to suit.

For the most part though i think its ace on my hardtail. Stuck with round on the full sus as that has bags of climbing traction and i sprint it more.

Thank you for your input so far,
I run a full suss 650b Enduro and ride all over the place. Entered Tweed Love in June.
My friends use mainly 30 tooth round rings and jut have an easy life on the ups compared to me as I’m no quicker but have to put in more effort on prolonged climbs.
As I said maxing out in top gear isn’t the main issue as it’s plenty fast enough even at bpw when the trail opens out.

I’d try a 32T if I were you, if it feels too easy or you don’t get on with it then either move up to 34T or go back to a round chainring.

Are they meant to help your knees now?

Not sure about being easier on the knees thing. The varying load on the knees is noticeable to me – or at least the feeling of variable load. I think they take a bit of getting used to, i’m not convinced of their claimed benefits, especially with mountain biking where you’re changing cadence and load constantly due to varying terrain, vs. a road bike where things are much more stable in terms of cadence. I can’t imagine they’re doing any harm or detrimental in any way, but just not convinced of the benefits.

It’s just the opinion of absolute black cynic-al, it’s worth a try if it might make me feel 10 years younger 🙂

If you go oval make sure you don’t put it on 90 degrees out 😀

Fortunately not possible for me as I’m xo direct mount:)

oops

deano8 – Member
It’s just the opinion of absolute black cynic-al, it’s worth a try if it might make me feel 10 years younger

There’s only 2 things guaranteed to do that. One’s probably socially unwise, the other is an eBike. 🙂

From the info for Absolute Black’s oval chainring on CRC…

Choosing correct size:
32T oval is best for someone currently riding 30 or 32T round chainring.
34T oval is best for someone currently riding 34 or 36T round chainring

It’s just the opinion of absolute black cynic-al, it’s worth a try if it might make me feel 10 years younger

It won’t!

You tried ?