woldranger

Hi there,

I've got a Specialized Sirrus 2005 https://www.bikepedia.com/QuickBike/B...rrus&Type=bike that's in need of a new drive train. Thanks to some great recommendations form folks on here I've got the chain (SRAM pc-830)and cassette (Shimano hg-50 12-23) sorted but still need to choose a chainset. Money is majorly tight and as I mainly use my bike for short hauls on the flat roads around here I don't need anything overly flashy.

From what I've seen out there (I'm in the UK) these two seem like the best options;
Stronglight Impact 28.38.48 for £30
https://www.chainreactioncycles.com/M...?ModelID=50639
and a Shimano Tiagra 4403 30.42.52 for £27
https://www.chainreactioncycles.com/M...?ModelID=13666

Would these be compatable with an 8 speed set up??

I've never swapped chainsets before and was wondering if I'd be better off sticking to a shimano model with regards to smooth/easy changes. The issue I have with the Stronglight is that the crankarms are 172.5mm.

I'd like to raise my gearing as opposed to reduce it, but I'm not sure if the road gearing of the shimano would be a little tall for me - I usually ride with the front on the outer ring (48t) and the back on the 5th, 6th or 7th gear (17t, 15t, 13t) and very rarely ever run on the smaller front rings as it's all pretty flat here. The draw of the is the availability of higher gearing and the option of using the middle ring. I've tried to read up on how to work out your gearing but haven't managed to suss it.

Any and all advice is appreciated!

AdelaaR

Both those chainsets are designed for 9-speed, which means that they'll have slightly narrower teeth than 8-speed.
This should however not be a problem and it should work, although chainwear may occur i guess.
I personaly have a triple 30-42-52 and find it superb ...
Do watch out though: your front derailleur is not constructed for 52 teeth cogs and it may not shift smoothly.
Secondly, the inclination of the bar on which the front derailleur resides is different on hybrid bikes compared to roadbikes.
What you need is what I used: A shimano R443 front derailleur, which is speciaficaly designed to run 52 teeth cogs on hybrid frames.

However, if you're not confident about this issue and find your current highest gear to be high enough ... I sugest simply sticking to the 48 teeth you have now and getting a specific 8-speed 48T triple like this: https://www.chainreactioncycles.com/M...?ModelID=41902

Arrowana

Adelaar, would I use that same FD for switching to a 52T triple on a MTB too? I remember putting a road triple and FD on an older MTB and it worked fine.

woldranger

Thanks for the lightening quick reply! I read a few pieces about 9 speed chainsets being ok for 8 speed set ups, but they didn't mention chainwear, so thanks for bringing that to my attention.

I'd have to check my front derailleur as the standard one had to be replaced last summer. I'd seen the R443's recommended for 8 speeds on a shimano tech guide, so I guess it's something I might have to look at.

I've seen the suntour 48t's on there, but amoungst other issues is the fact that they have 170mm crankarms.

I've been looking for quite some time on ebay for new/used cranksets, but after picking up a used one that "had no visible signs of wear" and was in a right state, I'll stick to looking for new ones - thankfully I got a full refund.

donm1967

Ranger - how much do you ride? I'm considering a new bike, Sirrus being on of them. But this post makes we wonder about durablity. Did you buy the base model?
Don

woldranger

I bought mine 2 summers ago, it's a 2005 model and it had had a fair bit of use. As for how much I ride, depends on the weather but I try and do a minimum of 100 miles a week. And yes, it's the base model. I'm happy with the bike, it's great for firing through traffic when commuting and has proved to be pretty durable with the state of some of the roads around here giving the rims a good work out.

dynaryder

FYI,all three of my old Sirrus Sport Discs(the universe does not want me riding these) were 8sp rear with 52/42/30 front. They were '04-'05,so you might need to look to eBay or another site for older parts.

woldranger

Did you have to change the front derailleur to accomodate the 52t triple front or was that the standard chainset for those bikes?

qmsdc15

You might need to change bottom bracket for one with a longer spindle, if the larger rings rub the frame with your current BB. Your front deraileur should work fine.

qmsdc15

Chains need to be replaced frequently to prevent cogs and chainrings from getting damaged. Nobody changes his or her chain often enough, and we all need new cogs when we do replace the chain. If you wait even longer to replace the chain, you'll need new rings too.

dynaryder

Stock setup. I also just remembered my Dew Deluxe is 52/42/30 w/8sp Megarange rear.

njkayaker

You should indicate what the numbers on the sprockets (rear) are.

You should run both setups through a gear calculator.

https://www.sheldonbrown.com/gears/

What is your normal cadence (pedal RPMs)?

woldranger

Numbers - as in teeth? If so, I made reference to them in my original posting. Otherwise, I've no idea what you mean.

I'll put me details into that calculator and see what it comes up with. As for cadence, around 85-90 ish.

njkayaker

Yes, teeth. You listed some of them, but not all of them.

It's likely that any set-up would have similar gears to what you usually ride with (a gear chart would tell you). The issue is whether you use the 8th gear (and whether you need a gear higher than that. If you never used the smallest front ring, you certainly would have no issues getting rid of it (ie, replacing it with something larger). If you need it, even "rarely", you are going to be out of luck (rarely) if you go with a larger smallest chainring. (If the hills are short, you could always stand or walk, I suppose.)

The gear calculator will show you what you'll get with the other setup. Your cadence seems reasonable (if it was much lower, it might make more sense to work on increasing it rather than buying new stuff).

Sixty Fiver

You chain rings will not care how many speeds your bike has as they are all designed for chain that has the same inner width and as chain gets narrower for 9 and ten speed drives the outer width of the chain gets reduced and the pins on the chain have to be flush to work with narrower cog spacings in the cassette.

Will work with gear inches and if you are familiar with old ten speed bikes they usually ran a 42/52 doouble with a 14-28 to give them a nice all around gearing with 40 gear inches being low enough to climb moderate hills and 100 gear at the top which was for descents and days when you had a tailwind.

For most people a single gearing of 70-75 gear inches seems optimal for cruising.

The 30/42/52 will give you a gear range of 35 - 116 gear inches while 28/38/48 gives you 32 - 107 so swapping will give you a bigger gain up top with very little change at the bottom but most people cannot spin 100 gear inches on the flats for any distance and anything over this is for descending and riding in a paceline.

What you may appreciate most is the 42 as with the 12-23 you get a nice range of 50 - 94 gear inches which is actually ideal for most flat riding.

I just changed my hybrid from a 28/38/48 with an 11-34 to a more compact 24/34/44 and an 11-30 cassette which retained my wall climbing low of 21 gear inches, reduced the top end to 107 from a nearly unuseable 117, and makes for smaller jumps between gears.

The 24 tooth granny is for towing and off roading and will never be needed on the road.

Sixty Fiver

Frames are designed with minimum and maximum chain ring allowances and if you have to install a wider bottom bracket you will throw off your chain line a little.

With modern cassettes offering 11 and 12 tooth cogs a good number of people have taken to running compact road doubles and this offers a very useable gear range, simplifies shifting, and improves chain line... the bb will have to be narrowed by 3-4 mm to get the optimal fit.

It is an ideal set up if you don;t have to do a lot of climbing and if you do a cassette with a 25 or 27 can be used to give a better low gear.