Replacing Biopace chainrings
 

Alright so my Bianchi has Shimano FC-1050 105 cranks. Velobase tells me it has 130mm BCD. I want to buy round chainrings for that crank.

Here is what I'm looking at buying. Are they compatible? Any other reason to avoid them?

52T
42T

Thanks

Don't have any experience with those particular chainrings but they should be compatible.

That seems like a lot for off-brand chainrings IMO. Could get some real Shimano ones for that price. Even slightly used you'll do well.

I changed my 42t biopace ring with a 39t round one and it makes a world of diff.on hills.The 39t was specialized.Works great.

there should be no issue using those chainrings, but I don't recommend that eBay seller. I bought stuff from them and waited more than a month for it to arrive. Sellers in Taiwan have good prices but ridiculous shipping times.

I had to do the same with my Shimano 600 Biopace. I never really shopped for chainrings and suprised on how expensive they were! I just kept waiting until a US seller had them. But Niagara cycles has good prices for SR rings. Try searching Amazon. Sometimes, the thing you need is sold through Amazon but fullfilled by Niagara cycles and Amazon charges less for shipping.

Great, thanks for the replies everyone. I am not too concerned about long shipping times, as it will be at least 2 months before I can actually go ride outside.

The same seller has SRAM powerglide chainrings 39T/53T for $75 shipped. Is that an okay deal, or should I look for something cheaper? Kind of feels like overkill to spend that much.

+1 on that. I just bought a new bottom bracket from them. Shipping was about $4 ordering via Amazon and more than twice that directly from Niagara's own site.

I bought a 39T Shimano chain ring off ebay to replace my 42T biopace for less $2. The shipping was more than the cost.

You posted a long time ago but had a question for you. I have a similar old bike and had a bike shop replace my freewheel to a 28t. My plan was to get a new crank and derailleur for under $100 ish. Was that 3t jump enough to get you up hills? I am literally passed by senior women on hills. That happened lol.

Have you ridden with your new 28 yet. That may be enough. However, 3 teeth in the front make a difference. Riding lots is more better.

The percentage change is what is important. Us you can go to 38 on a 130 bcd if you can find one. 42 to 39 is about 7 to 8 percent change a 38 would be 10. Its about a half step lower in terms of touring gears.

I have. It helped!! I was grateful and it was worth the $. I am in the Northeast, many rides in my area surpass 2K cumulative feet, and on this thing that is rough. It's a great workout for sure.

May I ask how you find the % change? 42/28 is 1.5 ratio and 39/28 is 1.39. Does the difference in ratio calculate percentage?

I ended up getting this crank with the same chainline as my current crank, and this DR if my current one has issues with the 34t chainwheel.

I have learned so much from the advice from people like you. Many thanks. If I **** the entire thing up, I am not out that much money lol. Only way you learn.

I've since switched to a triple,If you're in great shape you can do hills with relatively high gearing.But now older and fatter the lower the better!

On the same bike???
I am 41 and in great shape but would like my knees and tendons to not get injured. I die inside if I cannot stay active. At least with the lower gears, it's my choice to torture myself which I do plenty as it is.

Yes, you have the correct idea. There are online tools for this sort of thing. For example: Link

the percentage change in gears can be figured going up or down. Divide the lower into the higher and u get 1 plus the percentage change. Personally i usually just figure gear inches because i know what inches i can usually handle. As a 63 yo man who is definitly not that strong i have very low gears and never apologize for them.

Go for it. After an injury and illness in 2018 I was pretty weak. I replaced my 52/42 chainrings with 50/39, then a 38T small chainring, and swapped from a 7-speed 13-25 to 13-28 freewheel. Helped a lot on climbs and riding into stiff headwinds while I was getting back into shape.

I've put a set of 52/42 Biopace back on that bike, but will probably go back to the 50/39 or 50/38 chainring setup, with the 13-28 freewheel. The only thing I lose with that gear combo is I'm spun out on fast downhills with a tailwind. Not a big deal since I don't use that bike to chase Strava KOMs or PRs. I have another bike for that. I prefer to keep my steel road bike comfy for long rides on roller coaster terrain with lots of short, steep climbs.

Check out Vuelta chainrings. Best buy in top quality chainrings. I have them in 50T (ramped and pinned for better shifting) and 39 and 38 plain rings (no need for ramped and pinned small chainrings on most bike/shifter setups).

Tha that really helps. I'm still a little unclear on how to change chain rings but I think I see it. I just got a whole new crank set.

It's usually a 5mm Allen bolt on the outside and slotted lock nut on the inside that needs a special wrench like this to do the job properly. Some chainring bolts have Allen bolts on both sides, sometimes 5mm or 6mm.

With conventional round chainrings the orientation doesn't matter. With non-round eccentric chainrings (Biopace, Absolute Black and others), orientation of the elongated lobes is usually critical to best performance. However opinions differ about optimal position so some folks re-orient the elongated lobes to suit themselves. I've tried that with Biopace but eventually went back to the original factory orientation.

No I bought a bike(Lemond Tourmalet with an original triple.

Yeah, me too. And I use the 39 round as an inner. I also have a 3x9 Allez that is handy too when I don't feel man enough for the Italian steel 2x6 or 2x8. getting old can really suk sometimes.
JMO of course

Almost all my bikes have triples. I don’t see the point in trying to be heroic. Like you say, the triple has a 39T ring and you can choose that if you want to challenge yourself. If not, put it in the small ring and spin. Chris Froome has been known to use a 34-32 low gear in pro tour stages in recent years. I figure if he can use that, no gear I choose will be wimpy when adjusted for fitness level.

This really depends on what you mean by "hills" and what the terrain is like where you live. Around here, pretty much every ride I do finds me on at least one 15+% grade, and for every 10 miles of riding there's 1,000 to 1,500 feet of climbing. Although in my younger days I did this routinely (though painfully) with a 42-25 or 42-28 low gear, I now look back on that and think "what was I thinking?" I suggest that you plot out gears on a gear chart (here's a good one: https://ritzelrechner.de/ - set "Display" to "Gear Inches"). If you're doing hills like what I do you'll want a low gear below 30" unless you have legs like tree trunks. For modest hilly terrain a low gear is the mid to low 30s somewhere is alright for most people. Note that a 42-28 low gear is about 41".