Hey, all!
I'm not sure if this is the right thread to post about it, but I'm doing so since it's related to the topic and informative.
I'm a Trainee Engineer in Bangalore Metropolitan Transport Corporation (BMTC). I'm typing in a few parts of my weekly report when I was posted as Observer & Evaluator (OE) of the Tire Retreading Plant (TRP) of the BMTC Central Workshop, as a part of my training.
Do let me know if you have any queries!
In the manufacture of a new tire, approximately 75%-80% of the manufacturing cost is incurred in tire body and remaining 20%-25% in the TREAD, the portion of the tire which meets the road surface. Hence, by applying a new TREAD over the body of the worn tire, a fresh lease of life is given to the tire, at a cost which is less than 50% of the price of a new tire. This process is termed as*'tire retreading'.
However, the body of the used tire must have some desirable level of characteristics to enable retreading. Retreading cannot also be done if the tire has already been over used to the extent that the fabric is exposed/damaged. Retreading can be done more than once.
a) Types of Retreading :
Retreading can be done by the following two processes:
⦁ Conventional Process (also known as 'mould cure' or 'hot cure' process) - In this process a un-vulcanized rubber strip is applied on the buffed casing of the tire. This strip takes the pattern of the mould during the process of vulcanization.
⦁ Pressure Process ( also known as 'cold cure')- In this process a tread strip, where the pattern is already pressed and pressure is applied to the casing. It is bonded to the casing by means of a thin layer of specially compounded uncured rubber (known as cushion or bonding gum) which is vulcanized by the application of heat, pressure and time.
The present all India pattern, by type of retreading, is as follows : Pressured - 50%, Conventional 50%.
Retreading is primarily done in the Truck and Bus tire segment. On an average a Truck/Bus tire is retreaded 1.5 times. At present only 3-4 large companies are in the organized sector of tire retreading. Organized sector is classified as that comprising of companies which operate through the franchisee route.
b) International vs Indian Standards in Tire Retreading : Similarities & Differences :
Similarities
As is the experience in other parts of the world, tire retreading in India has gained greater acceptance in the commercial segment, especially truck/bus and light commercial vehicle (LCV) tires, due to operational savings.
The share of passenger car tire retreading is on the decline due to several factors,viz. fitment of radial tires as OE fitment giving increased mileage (encouraging owners to go in for new radial tires at the time of replacement, strong preference of improved aesthetics of new generation of passenger cars (and hence new tires) and above all, a growing concern for safety (due to driving at increased speeds.
Differences
In the developed countries retreading, by and large, is only through pressured methods, whereas the share of hot/conventional retreading in India is high 50%, with the share of hot/conventional retreading in select segments, like farm tires, being considerably higher.
The bonding gums and rubber treads used in the Tire Plant were bought from Cochin Rubbers, a very reputed brand in this industry. A total of 96 tires were retreaded during the duration of my stay in this section. A majority of the tires were for the Tata/Ashok Leyland buses with no Tata-Marcopolo bus' tyre being brought in.
Sources for aforementioned information (Big thanks to them!) :
1. Wikipedia.
2. Howstuffworks.
2. Cochin Rubbers Guidebook.
3. TRP Operations Manual.
FIGURES :
1st - The primary heating chamber for the re-treaded tyres.
2nd - The secondary heating chamber. A temperature of 125 degrees celsius is maintained inside for a stipulated period of time.
3rd - The brand new treads laid out for resoling.
4th - A retreaded tyre ready for inspection, after which it'll be sent to respective depots for fitting, depending on demand.