SRAM PG850 8 Speed Cassette
- ShowProduct Information The SRAM PG850 8 Speed cassette is perfect for 8-speed steeds, offering smooth shifting and great pe... read more
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Product Description
The SRAM PG850 8 Speed cassette is perfect for 8-speed steeds, offering smooth shifting and great performance. The race-proven design and durable, chrome-plated finish will keep you rolling for years.
Occasionally, without notice, manufacturers change product design and/or specifications.
Casettes Guide
Cassette Guide
A cassette is the cluster of gears that are attached to the rear hub of your bike. The derailleur shifts the chain up and down the cassette changing gears as you ride.
There are many different sizes and types of cassette available. A cassette will wear over time and will need replacing. To easily find a replacement, the speed and number of teeth must be matched to your existing cassette to ensure compatibility with your shifter and derailleur.
Cassette or Freewheel?
The rear cluster of cogs is attached to the wheel in one of two different ways. To replace these cogs you will need to establish if you have a cassette or a freewheel.
Freewheel
A freewheel is mainly used on older bikes from before the mid-'90s or on bikes that have 5, 6 or 7-speed cogs. A freewheel is a screw-on type, the ratchet freewheel mechanism is housed inside the cogs and is supplied as one complete unit. If your rear hub is designed for a screw-on freewheel then a cassette can not be fitted.
Cassette
A cassette will have more gears than a freewheel, housing 7, 8, 9, 10, 11, 12 or even 13 gears. A cassette does not include the ratchet mechanism that is found in a freewheel, instead, the ratchet mechanism is part of the rear hub. The part of the rear hub that houses the freewheel is known as the freehub. The cassette fits over the freehub, the most common way is that it slides onto a splined freehub and secures with a lockring.
What size?
The size of the cassette is measured in teeth and the number of speeds. The teeth are the small spikes that stick out on each cog. The smaller the cog (and therefore the number of teeth) the harder the gear is to pedal, to be used when going fast. The larger the cog the easier the gear is to pedal, to be used when climbing a hill and going slow.
When replacing your cassette it is best to count the number of teeth on the largest and smallest cogs, and match the replacement to these sizes and total speeds to ensure compatibility with your existing derailleur. Any particular rear derailleur will have a maximum capacity, so you cannot always add a larger cassette to get easier gearing without also changing the derailleur to suit the larger size.
Mountain Bike Cassettes
Mountain bike cassettes have seen a big change in the last few years. With the advent of 1x drivetrains that use a single cog on the chainset, cassettes have got much larger so the same gear range can be offered as was given by 2x drivetrains.
10, 11 and now 12-speed cassettes are common on mountain bikes. To have the low gearing needed for the steep climbs and rough terrain found on MTB trails, most cassettes will use a 42 tooth or larger ring for 1st gear. Shimano's 12 speed and SRAM's Eagle cassettes use a massive 51 or 52 tooth 1st gear.
Most 9, 10 and 11-speed cassettes still fit the tried and tested splined HG freehub design originally made by Shimano, though the newest 12-speed Shimano cassettes and SRAM cassettes that utilise a 10 tooth small cog use specialised freehub designs, namely Microspline for Shimano and XD for SRAM.
Road Bike Cassettes
Road bikes use smaller more compact cassettes than mountain bikes. The average speed of a road bike is much higher than a mountain bike, the vast majority of road bikes also use 2x drivetrains that give a good gear range so a small and light cassette can be used. By packing the gears in a smaller cluster there is less of a jump between each gear, meaning the ideal cadence can be kept as the gradient changes.
The largest sprocket is much smaller than those on MTBs. For climbing and very hilly routes, a cassette with a 1st gear of 32 teeth can be used, but the most common size seen is a 25 tooth large cog, down to a 12 tooth small cog, known as a 12-25.
Most modern road bikes will use 10 or 11-speed cassettes, though there is 12 speed offered by Campagnolo and SRAM on the most high-end groupsets.
Removal and fitting
Removal and fitting of a cassette is a relatively simple task that can be done at home, though there are special tools needed. There are also some differences between different brands of a cassette.
Please see our How To Remove And Fit A Cassette guide with videos for more information.
Delivery & Guarantee
UK Delivery Information
International Deliveries – Temporarily Suspended 11/11/20
Note: We are still offering deliveries to the Isle of Man, Scottish Highlands, Scottish Islands, Channel Islands, Isle of Wight, Jersey and Guernsey.
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Please keep checking the TNT tracking for further updates. On behalf of TNT we apologise for any delay and inconvenience this may cause.
We are committed to offering fast and free delivery, whether you're ordering bikes, accessories or clothing. Our standard delivery service is FREE in the UK, regardless of the size and on all orders over £20.
Please note that bulky products and bikes shipped to outlying UK regions are excluded from free shipping.
Please note that Pre-Order dates can sometimes change due to updated stock information.
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Returns & Warranty
It's easy to return a product with our 365 day, hassle free returns.
We will give you a full refund on any item that is returned to us unused/unfitted, in a resaleable condition and in its original packaging (where possible).
Please note: For hygiene reasons, we cannot accept returns of facemasks, undershorts or underwear if the item has been removed/unsealed from its original packaging.
If your item develops a fault or arrives damaged, please contact us first so we can resolve the issue for you as quickly as possible.
For more information please visit our Returns & Warranty page.
