beatifik

so, would a casual, 130lb rider be able to benefit from upgrading to the Grand Mighty crankset over the standard 75's? will they have a longer life? a lot more responsive?

they will ridden on the street ONLY. this bike will never be on a track. they're going on a Bomber Pro Keirin frame if it makes any difference...

i'm building up a bike and was just wondering if they were worth the extra dough?

thanks.

drac_vamp

you won't notice any difference at all.

11.4

I've got both. The answer is ... probably not.

What does the Grand Mighty have? Most of the cost is in the forging. Instead of something like three forging passes on the 75, the Grand Mighty has an amazing 26. This means it's much stiffer and individual parts such as the spider and the area around the pedal threads are much more resistant to impact damage or to flexion. If you fall (or get hit) hard enough to snap your crank, you probably have other bigger worries.

The finish on the Grand Mighty is mighty Mighty. It's a gorgeous finish and happens to be extremely resistant to corrosion, oxidation blooms, and the like. So it'll keep looking gorgeous while the 75 will look a bit punky after a while. And if you use toe straps, the clear anodized finish on the 75 will disappear in days, but the gold Grand Mighty finish will last a lot longer.

The milling of the square taper on the Grand Mighty is more precise (both done to size more accurately and also more precisely in the center of the crank) than on the 75. This plus the superior forging means you can take it on and off a lot more than a 75 before it doesn't quite go on as straight, and it is more likely to give you a truly centered chainring (people ***** about chainrings not being round when the problem is usually that the square taper was milled off-center, causing the whole shebang to be off-center, and no change in chainring will correct it).

It's up to you which one you get at this point. Personally I like the Grand Mighty and its durable finish and precision. Plus I do race track and it is quite definitely stiffer, although you have to put out a lot of watts and feel really good on an evening to be able to notice that difference.

sers

tomity said that keirin riders prefer the grand mighty because it is more flexy.

TacoPropelled

Didn't Tomity say the opposite?

ka12na

Word?

Sin-A-Matic

Business Cycles confirms what 11.4 said. It seems odd that they would be more flexy...

TacoPropelled

I thought Tomity said that the grand mightys were liked less because of their flexiness.

Sin-A-Matic

Oh, haha. Can a crankset be stiff and flexy at the same time?

beatifik

wow, this thread has gotten confusing fast...

i'm gonna take 11.4's information as fact and all of this second-hand tomity info as rumors.

sers

unfortunately i can't do a search now, but i started a thread a while back asking why nagasawas come with 109mm square taper bb's installed, since the only current production cranks that fit that are the suginos. here's what tomity said:

Hi!! This is Tomity
90% of Japan nearby professinal Keirin rider uses the crank of old square-taper type.
Therefore, Mr. nagasawa equips it with bb of hatta R9400.

The crank of most square-taper type of NJS suits bb of hatta R9400.
Professional Keirin rider doesn't frequently remove the crank usually.

The reason is that square-taper of the crank extends.
The possibility of it that the chain line shifts is high.

There are a lot of fans because Sugino grand mightys is more flexible than Sugino 75s.
Because Shimano octalink splined system should exchange bb, popularity is low.

However, Shimano octalink splined system is a repetition of the installation of the crank and
doesn't have the change in the chain line.

Were you able to understand?
Tomity


onetwentyeight asked for confirmation:

Tomity - Are you saying that the Grand Mighty's are not as stiff as 75s??

PS. I got my tomity cog, it is lovely, thanks!

Tomity confirmed:

Yes!! Almost rider says its opinion
The reason is related to the sectional area of the crank.

In it, I am very honored. Thank you!!

here's the thread

11.4

Odd. I have both and the Grand Mighty isn't any thinner in any dimension compared to a 75. Both are solid aluminum, and the extra forging steps on the Grand Mighty should have created extra strength and stiffness. The only metal that's thinner on the Grand Mighty is that the spider and the crank arms have a little bit of the corners shaved down, but this isn't likely to make it more flexible.

pitboss

bring your bike and your brain to Northbrook. I'll ride laps with ya!

Renz

Anyone know why a flexier crankset might be the choice for keirin champions?
My uneducated guess would be the slight flex could be easier for the legs at full-tilt, and could act like a spring "storing" energy on the downstroke and returning it on the pedal upstroke. Maybe.

fatbat

perhaps "flexible" in this context means that you can take the cranks on and off the BB more without incuring damage than with the 75's.

sers

i doubt it. "not as stiff" is pretty explicit in the above conversation.