kato12

Would there be any advantage to upgrade my crank from a sram S900 road 46/38,to a Sram black red compact crankset 50/34.Iam trying to turn cycocross bike into a road bike,without trying to buy a new bike.thanks

Wolfwerx

That's up to you, and the type of riding you want to do. Maybe you could just change the chainrings instead of the whole crankset.
If it were mine, I would probably leave the 46 and swap that 38 for something in the 32-34 tooth range, but it wouldn't be something too pressing for me.

kato12

All iam doing right know is road riding.

bigfred 

Is the 46/38 failing to meet your requirements in some way? Not low enough or high enough gearing? It (the 46/38) will provide closer gearing and more overlap between chainrings than the 50/34 will. The 50/34 will of course provide added range at both the top and bottom. As has already been mentioned, if you only need more gearing in one direction or the other, you could simply swap out the chain rings.

If, however, you're looking for some performance improvement. I have always bucked the majority opinion and believe that cranks, as rotating weight and the heaviest component on a bike after the wheels, are one of the more noticable places to save weight (second to wheels and tires).

But, have you replaced the tires yet? If so, with what? And, what has your observation of that upgrade been?

Wolfwerx

That doesn't really answer the question.
Fast or slow?
Hills or flat?
Centuries or around-the-block?

What are your specific plans and/or desires? What kind of budget are you hoping to stay within? If all you are wanting to do is have something labeled "road" versus "cyclocross" then knock yourself out, but if there is no specific complaint about your gearing, then there is no real reason to swap out the crankset. That 46 tooth ring is more than enough for most people, in reality. At the other end, unless you are climbing hills, you could probably live with the 38 and a good spread on your cogs. As I mentioned above, you could change the small chainring individually if you need to get low, and save a lot of expense and potential labor.

FWIW, cyclocross bikes make good road bikes for Clydes... which I'm just assuming you are since you posted here.

rearviewbeer

Also depends what you have in the rear, but you should be able to just change the rings in the front - no? 46 in front is not much for road cycling, even with an 11 tooth on the bottom in the rear. I think most people with doubles go with a 50/34 combo. Might want wider range in rear if you have any hills where you ride, 11 - 28/32.

Wolfwerx

Great idea.



How is 46 teeth "not much for road cycling"?

kato12

Not have replaced rims and tires yet,was thinking on bontrager rims,trying to get better on hills and get a little faster.the cassette is 11/28.

zonatandem

We run 32/48 chainrings and 11/34 10-speed cassette on our tandem.

bigfred 

Replace the 34mm tires with something in the 25mm-28mm range first. You've never confirmed if you have the Ultegra wheels or not. If so, you'll need to spend a fair bit of coin to get much lighter and still be clyde worthy. A custom wheel could probably be built stiffer, at around the same weight. I know there are some clydes on here that have had reasonable luck with Bontrager wheels/rims, but, they (Bontragers) are not renowned for being particularly durable. Why the change from considering the Sram S30 AL?

With the exception of upgrading your tires, the improvement you seek is not to be found in trading components.

kato12

Iam looking at the bontrager aeolus 5 d3 rims,with a 25 mm tire.also i have the ultegra wheels.

bigfred 

In theory those will save you 100 grams off the weight of your current wheels and provide an aero advantage at speeds in excess of 20mph. If you're averaging 20+mph on your rides and have a spare grand to spend, what the heck, give 'em a try.

I was thinking about my responses to your questions about wheels and cranks. If you were to rephrase your question to something along the lines of, "I have XXXX dollars burning a hole in my pocket. What's the best place I could spend that money to improve my speed, especially climbing?"

I would reply, if you don't already have one, purchase a power compatible computer with HRM and cadence and put it to good use. Even without the power function for now, training with HR and cadence will go a long way toward helping improve performance. Learning where your threshold is, attempting to spend an hour per week above that point during training, and riding right up to that limit but not beyond (except during special circumstances) during group rides or those that you're paying attention to your time on will make a huge difference in your cycling.

Then, with a power compatible computer head on your bike, the next upgrade if performance is your concern would be to consider either power cranks or a rear wheel built around a powertap hub.

You've never said what frame and wheels your friend lent you that has resulted in your dissatisfactioin with the Cronus CX Ult. Knowing that could really help frame any other responses.

kato12

thanks bigfred for the responses.they are greatly appreciated.now i know why i don't post on a lot of forums,and just read them instead.

skilsaw

[QUOTE=Wolfwerx;How is 46 teeth "not much for road cycling"?[/QUOTE]

Almost all road bikes have a 50 tooth or larger big chainring. But to use it much, you need to be physically fit and want to go fast. I tour pulling a loaded Burley trailer and have put a 48/38/28 on my bike. But to each, his own.


I will parrot the advice already given. Match the chainring choice to your style of riding, terrain and level of fitness. But above all, have fun.

Buck_O

The Power Glide Chainrings are all the same for Apex, Rival, Force, and S900. I would just get new road compact rings rings for your BCD, and leave it at that.

At this point, as bigfred said, unless you are pushing 20+ MPH average, just put some wider road wheels on your current wheels (likely 28mm), and see how it feels. You may actually prefer the softer ride of the larger tires anyway. Having a narrower tires doesnt automatically = faster.

Wolfwerx

The fact that "Almost all road bikes have a 50 tooth or larger big chainring" doesn't mean that it's really necessary. Just because that's what most bikes have doesn't mean that's what most riders can really use.
Again, how is a 46 tooth big ring "not much for road cycling"? Can you spin out a 46/11 on anything but a crazy-steep hill?

Edited to add: I don't mean for that to sound rude, I'm legitimately asking.

Yes, I know, that was my point.

bigfred 

Sorry about that. Let me take another swing at your question.

Ans.: Possibly, depending on your use of the bike, the terrain you are cycling on and your fitness level.
The 50/34 will provide a greater overall gearing range, both high and low. But, will require more shifting of the back when you move between front chain rings. If you are a visual charts and graphs person, visit here:
https://www.gear-calculator.com/#KB=3...5&UF=2099&SL=2

There will also be a slight weight savings. The Red crank weight is listed w/o bb but taking 50-100 grams into account depending upon whether it's bb30 or gxp and discounting any difference in the CX ring set up your weight savings will be around 100-150 grams. Many discount crank weight savings as unnoticable. I'm not one of them. As rotating weight and a reasonable heavy component in the overall bike weight, I feel they are an excellent and easy area to save weight. However, weight savings sometimes comes with other consequences and in the case of cranks, that is flex. If you go visit the WeightWeenies you'll learn that their current favorite light crank is the cannondale hollogram SLsi(or somesuch alphabet soup). They are also excited about the new 2012 Red and and believe it may provide just as much stiffness. The majority opinion overthere seems to be that either is more than adequate for a 145lb rider:-)

Depending upon your height and leg length an crank arm length change might make a more noticable change than any weight savings would. Take a look at any of the internet articles about proportional crank length and consider using one at the long end of your range to provide additional leverage for climbing.

No matter how much you spend on wheels and cranks, you will not change the character of your cross frame.



I have a friend who is/was a stronger rider than me. But, they could never keep up when on their cross bike with 34mm tires. With 25mm tires on the same bike it was a slightly different story. After changing out the tires, getting better on hills is largely about power to weight. Plain and simple. If you're struggling to maintain in excess of 60rpm cadence with your current 38 tooth small ring, a 34 will make the hills easier but not neccessarily as faster. 39/53 with an 12-25 is sort of the classic road racing all around set up. You've got just a little less gearing than that on your bottom end. But, not much. To effectively push the 38-28 up anything over 10% you'll need to be pretty fit. So, a 34 ring may be better. I cetainly believe them to be for the majority of recreational cyclists. The tradeoff being that they require more shifting of both the front and rear.

I was mistaken when I saw the price at $1200-1400. I thought that was for the set. It's not. That's per wheel. The set is going to be close to $3,000. That plus a Red series crank will purchase you a very nice road specific racing bike.

I hope you find that answer more palatable and continue to post.